Technical Evaluation Report Related to Order Modifying Licenses with Regard... for Mitigation Strategies for Beyond-Design-Basis External Events, EA-12-049

Technical Evaluation Report Related to Order Modifying Licenses with Regard... for Mitigation Strategies for Beyond-Design-Basis External Events, EA-12-049

Technical Evaluation Report Related to Order Modifying Licenses with Regard to Requirements
for Mitigation Strategies for Beyond-Design-Basis External Events, EA-12-049
Revision 1
January 23, 2014
Virginia Electric and Power Company
North Anna Power Station, Units 1 & 2
Docket Nos. 50-338 and 50-339
Prepared for:
U.S. Nuclear Regulatory Commission
Washington, D.C. 20555
Contract NRC-HQ-13-C-03-0039
Task Order No. NRC-HQ-13-T-03-0001
Job Code: J4672
TAC Nos.: MF0998 and MF0999
Prepared by:
Mega-Tech Services, LLC
11118 Manor View Drive
Mechanicsville, Virginia 23116
Technical Evaluation Report
North Anna Power Station, Units 1 & 2
Order EA-12-049 Evaluation
1.0
BACKGROUND
Following the events at the Fukushima Dai-ichi nuclear power plant on March 11, 2011, the
U.S. Nuclear Regulatory Commission (NRC) established a senior-level agency task force
referred to as the Near-Term Task Force (NTTF). The NTTF was tasked with conducting a
systematic, methodical review of NRC regulations and processes to determine if the agency
should make additional improvements to these programs in light of the events at Fukushima
Dai-ichi. As a result of this review, the NTTF developed a comprehensive set of
recommendations, documented in SECY-11-0093, “Near-Term Report and Recommendations
for Agency Actions Following the Events in Japan,” dated July 12, 2011. These
recommendations were enhanced by the NRC staff following interactions with stakeholders.
Documentation of the staff’s efforts is contained in SECY-11-0124, “Recommended Actions to
be Taken without Delay from the Near-Term Task Force Report,” dated September 9, 2011, and
SECY-11-0137, “Prioritization of Recommended Actions to be Taken in Response to Fukushima
Lessons Learned,” dated October 3, 2011.
As directed by the Commission’s staff requirement memorandum (SRM) for SECY-11-0093, the
NRC staff reviewed the NTTF recommendations within the context of the NRC’s existing
regulatory framework and considered the various regulatory vehicles available to the NRC to
implement the recommendations. SECY-11-0124 and SECY-11-0137 established the staff’s
prioritization of the recommendations.
After receiving the Commission’s direction in SRM-SECY-11-0124 and SRM-SECY-11-0137,
the NRC staff conducted public meetings to discuss enhanced mitigation strategies intended to
maintain or restore core cooling, containment, and spent fuel pool (SFP) cooling capabilities
following beyond-design-basis external events (BDBEEs). At these meetings, the industry
described its proposal for a Diverse and Flexible Mitigation Capability (FLEX), as documented in
Nuclear Energy Institute’s (NEI) letter, dated December 16, 2011 (Agencywide Documents
Access and Management System (ADAMS) Accession No. ML11353A008). FLEX was
proposed as a strategy to fulfill the key safety functions of core cooling, containment integrity,
and spent fuel cooling. Stakeholder input influenced the NRC staff to pursue a more
performance-based approach to improve the safety of operating power reactors relative to the
approach that was envisioned in NTTF Recommendation 4.2, SECY-11-0124, and SECY-110137.
On February 17, 2012, the NRC staff provided SECY-12-0025, “Proposed Orders and Requests
for Information in Response to Lessons Learned from Japan’s March 11, 2011, Great Tohoku
Earthquake and Tsunami,” to the Commission, including the proposed order to implement the
enhanced mitigation strategies. As directed by SRM-SECY-12-0025, the NRC staff issued
Order EA-12-049, “Order Modifying Licenses with Regard to Requirements for Mitigation
Strategies for Beyond-Design-Basis External Events.”
Guidance and strategies required by the Order would be available if a loss of power, motive
force and normal access to the ultimate heat sink needed to prevent fuel damage in the reactor
and SFP affected all units at a site simultaneously. The Order requires a three-phase approach
for mitigating BDBEEs. The initial phase requires the use of installed equipment and resources
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to maintain or restore key safety functions including core cooling, containment, and SFP
cooling. The transition phase requires providing sufficient portable onsite equipment and
consumables to maintain or restore these functions until they can be accomplished with
resources brought from offsite. The final phase requires obtaining sufficient offsite resources to
sustain those functions indefinitely.
NEI submitted its document NEI 12-06, “Diverse and Flexible Coping Strategies (FLEX)
Implementation Guide” in August 2012 (ADAMS Accession No. ML12242A378) to provide
specifications for an industry-developed methodology for the development, implementation, and
maintenance of guidance and strategies in response to Order EA-12-049. The guidance and
strategies described in NEI 12-06 expand on those that industry developed and implemented to
address the limited set of beyond-design-basis external events that involve the loss of a large
area of the plant due to explosions and fire required pursuant to paragraph (hh)(2) of
10 CFR 50.54, “Conditions of licenses.”
As described in Interim Staff Guidance (ISG), JLD-ISG-2012-01, “Compliance with Order
EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for
Beyond-Design-Basis External Events,” the NRC staff considers that the development,
implementation, and maintenance of guidance and strategies in conformance with the
guidelines provided in NEI 12-06, Revision 0, subject to the clarifications in Attachment 1 of the
ISG are an acceptable means of meeting the requirements of Order EA-12-049.
In response to Order EA-12-049, licensees submitted Overall Integrated Plans (hereafter the
Integrated Plan) describing their course of action for mitigation strategies that are to conform
with the guidance of NEI 12-06, or provide an acceptable alternative to demonstrate compliance
with the requirements of Order EA-12-049.
2.0
EVALUATION PROCESS
In accordance with the provisions of Contract NRC-HQ-13-C-03-0039, Task Order No.
NRC-HQ-13-T-03-0001, Mega-Tech Services, LLC (MTS) performed an evaluation of each
licensee’s Integrated Plan. As part of the evaluation, MTS, in parallel with the NRC staff,
reviewed the original Integrated Plan and the first 6-month status update, and conducted an
audit of the licensee documents. The staff and MTS also reviewed the licensee’s answers to
the NRC staff’s and MTS’s questions as part of the audit process. The objective of the
evaluation was to assess whether the proposed mitigation strategies conformed to the guidance
in NEI 12-06, as endorsed by the positions stated in JLD-ISG-2012-01, or an acceptable
alternative had been proposed that would satisfy the requirements of Order EA-12-049. The
audit plan that describes the audit process was provided to all licensees in a letter dated August
29, 2013 from Jack R. Davis, Director, Mitigation Strategies Directorate (ADAMS Accession No.
ML13234A503).
The review and evaluation of the licensee’s Integrated Plan was performed in the following
areas consistent with NEI 12-06 and the regulatory guidance of JLD-ISG-2012-01:
•
•
•
Evaluation of External Hazards
Phased Approach
 Initial Response Phase
 Transition Phase
 Final Phase
Core Cooling Strategies
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•
•
•
Spent Fuel Pool Cooling Strategies
Containment Function Strategies
Programmatic Controls
 Equipment Protection, Storage, and Deployment
 Equipment Quality
The technical evaluation (TE) in Section 3.0 documents the results of the MTS evaluation and
audit results. Section 4.0 summarizes Confirmatory Items and Open Items that require further
evaluation before a conclusion can be reached that the Integrated Plan is consistent with the
guidance in NEI 12-06 or an acceptable alternative has been proposed that would satisfy the
requirements of Order EA-12-049. For the purpose of this evaluation, the following definitions
are used for Confirmatory Item and Open Item.
Confirmatory Item – an item that is considered conceptually acceptable, but for which
resolution may be incomplete. These items are expected to be acceptable, but are
expected to require some minimal follow up review or audit prior to the licensee’s
compliance with Order EA-12-049.
Open Item – an item for which the licensee has not presented a sufficient basis to
determine that the issue is on a path to resolution. The intent behind designating an
issue as an Open Item is to document items that need resolution during the review
process, rather than being verified after the compliance date through the inspection
process.
Additionally, for the purpose of this evaluation and the NRC staff’s interim staff evaluation (ISE),
licensee statements, commitments, and references to existing programs that are subject to
routine NRC oversight (Updated Final Safety Analysis Report (UFSAR) program, procedure
program, quality assurance program, modification configuration control program, etc.) will
generally be accepted. For example, references to existing UFSAR information that supports
the licensee’s overall mitigating strategies plan, will be assumed to be correct, unless there is a
specific reason to question its accuracy. Likewise, if a licensee stated that they will generate a
procedure to implement a specific mitigation strategy, assuming that the procedure would
otherwise support the licensee’s plan, this evaluation accepts that a proper procedure will be
prepared. This philosophy for this evaluation and the ISE does not imply that there are any
limits in this area to future NRC inspection activities.
3.0
TECHNICAL EVALUATION
By letter dated February 28, 2013, (ADAMS Accession No. ML13063A182), and as
supplemented by the first six-month status report in letter dated August 28, 2013 (ADAMS
Accession No. ML1324A012), Virginia Electric and Power Company (the licensee or Dominion)
provided the North Anna Power Station Units 1 & 2 (North Anna) Integrated Plan for compliance
with Order EA-12-049. The Integrated Plan describes the strategies and guidance under
development for implementation by North Anna for the maintenance or restoration of core
cooling, containment, and SFP cooling capabilities following a BDBEE, including modifications
necessary to support this implementation, pursuant to Order EA-12-049. By letter dated August
28, 2013 (ADAMS Accession No. ML13234A503), the NRC staff notified all licensees and
construction permit holders that the NRC staff is conducting audits of their responses to Order
EA-12-049. That letter described the process used by the NRC staff in its review, leading to the
issuance of an interim staff evaluation and audit report. The purpose of the staff’s audit is to
determine the extent to which the licensees are proceeding on a path towards successful
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implementation of the actions needed to achieve full compliance with the Order.
3.1
EVALUATION OF EXTERNAL HAZARDS
Sections 4 through 9 of NEI 12-06 provide the NRC-endorsed methodology for the
determination of applicable extreme external hazards in order to identify potential complicating
factors for the protection and deployment of equipment needed for mitigation of BDBEEs
leading to an extended loss of all alternating current (ac) power (ELAP) and loss of normal
access to the ultimate heat sink (UHS). These hazards are broadly grouped into the categories
discussed below in Sections 3.1.1 through 3.1.5 of this evaluation. Characterization of the
applicable hazards for a specific site includes the identification of realistic timelines for the
hazard; characterization of the functional threats due to the hazard; development of a strategy
for responding to events with warning; and development of a strategy for responding to events
without warning.
3.1.1
Seismic Events.
NEI 12-06, Section 5.2 states:
All sites will address BDB [beyond-design-basis] seismic considerations in the
implementation of FLEX strategies, as described below. The basis for this is
that, while some sites are in areas with lower seismic activity, their design basis
generally reflects that lower activity. There are large, and unavoidable,
uncertainties in the seismic hazard for all U.S. plants. In order to provide an
increased level of safety, the FLEX deployment strategy will address seismic
hazards at all sites.
These considerations will be treated in four primary areas: protection of FLEX
equipment, deployment of FLEX equipment, procedural interfaces, and
considerations in utilizing off-site resources.
The licensee’s screening for seismic hazards, as presented in their Integrated Plan, has
screened in this external hazard. The licensee confirmed on page 1 of the Integrated Plan that
a site-specific assessment for North Anna provides the development of strategies, equipment
lists, storage requirements, and deployment procedures for the conditions and consequences of
seismic events. The licensee also stated that the seismic re-evaluation pursuant to the
10 CFR 50.54(f) letter of March 12, 2012 had not been completed and therefore was not
assumed in their Integrated Plan.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to screening for
seismic hazards, if these requirements are implemented as described.
3.1.1.1 Protection of FLEX Equipment – Seismic Hazard
NEI 12-06, Section 5.3.1 states:
1. FLEX equipment should be stored in one or more of following three
configurations:
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a. In a structure that meets the plant’s design basis for the Safe Shutdown
Earthquake (SSE)(e.g., existing safety-related structure).
b. In a structure designed to or evaluated equivalent to [American Society of
Civil Engineers] ASCE 7-10, Minimum Design Loads for Buildings and
Other Structures.
c. Outside a structure and evaluated for seismic interactions to ensure
equipment is not damaged by non-seismically robust components or
structures.
2. Large portable FLEX equipment such as pumps and power supplies should
be secured as appropriate to protect them during a seismic event (i.e., Safe
Shutdown Earthquake (SSE) level).
3. Stored equipment and structures should be evaluated and protected from
seismic interactions to ensure that unsecured and/or non-seismic
components do not damage the equipment.
On page 17 of the Integrated Plan the licensee stated that a study is in progress to determine
the design features, site location(s), and number of equipment storage facilities. The final
design for BDB equipment storage will be based on the guidance contained in NEI 12-06,
Section 11.3, Equipment Storage. The licensee completed the BDB equipment storage study
as documented in the completed Open Item #6 of its six-month status report. Staff review of the
results of this study is identified as Confirmatory Item 3.1.1.1.A in Section 4.2 below.
The licensee’s commitment to meet the storage structure considerations of NEI 12-06, Section
11.3 will conform to the storage structure considerations of Section 5.3.1 for the seismic hazard.
On page 29, 56, and 64 of the Integrated Plan the licensee stated that the BDB pumps,
necessary hoses and fittings are protected from seismic events while stored in the BDB
Storage Building(s) or in protected areas of the plant.
On page 64 of the Integrated Plan the licensee stated that the BDB portable diesel generators,
necessary cables and connectors will be protected from seismic events while stored in either
the BDB Storage Building(s) or in seismic protected areas of the plant.
The licensee’s plan did not address the securing of large portable equipment to protect them
during a seismic event or to ensure unsecured and/or non-seismic components do not damage
the equipment during a seismic event as specified by NEI-12-06, Section 5.3.1 considerations 2
and 3. During the audit process, the licensee stated that the storage building will be equipped
with tie-downs to ensure FLEX equipment is protected from seismic events. Fire protection and
HVAC within the storage building is being seismically installed. Lighting, conduits, and fire
detection is not considered a threat to damage the FLEX equipment.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to the protection of FLEX equipment seismic hazard, if these requirements are implemented as described.
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3.1.1.2 Deployment of FLEX Equipment - Seismic Hazard
NEI 12-06, Section 5.3.2 states:
The baseline capability requirements already address loss of non-seismically
robust equipment and tanks as well as loss of all AC. So, these seismic
considerations are implicitly addressed.
There are five considerations for the deployment of FLEX equipment following a
seismic event:
1. If the equipment needs to be moved from a storage location to a different
point for deployment, the route to be traveled should be reviewed for potential
soil liquefaction that could impede movement following a severe seismic
event.
2. At least one connection point for the FLEX equipment will only require access
through seismically robust structures. This includes both the connection point
and any areas that plant operators will have to access to deploy or control the
capability.
3. If the plant FLEX strategy relies on a water source that is not seismically
robust, e.g., a downstream dam, the deployment of FLEX coping capabilities
should address how water will be accessed. Most sites with this
configuration have an underwater berm that retains a needed volume of
water. However, accessing this water may require new or different
equipment.
4. If power is required to move or deploy the equipment (e.g., to open the door
from a storage location), then power supplies should be provided as part of
the FLEX deployment.
5. A means to move FLEX equipment should be provided that is also
reasonably protected from the event.
On page 100 of the Integrated Plan, the licensee stated that preferred travel pathways for FLEX
equipment movement will be determined using the guidance contained in NEI 12-06. The
pathways will attempt to avoid areas with trees, power lines, and other potential obstructions
and will consider the potential for soil liquefaction. However, debris can still interfere with these
preferred travel paths. Debris removal equipment will be kept in the BDB Storage Building(s) so
that it is protected from the severe storm, earthquake and flood hazards. Therefore, the debris
removal equipment remains functional and deployable to clear obstructions from the travel
pathways to the BDB equipment's deployed location(s). The stored BDB equipment includes
tow vehicles (small tractors) equipped with front-end buckets and rear tow connections in order
to move or remove debris from the needed travel paths. A front-end loader will also be
available to deal with more significant debris conditions.
On pages 30, 31, 35, 44, 45, 46, 57, 58, 65, 66, 68, 74, and 76 of the Integrated Plan, in
the sections describing protection of connections, the licensee details information as to
how at least one connection point for FLEX equipment will only require access through
seismically robust structures.
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On page 26 of the Integrated Plan the licensee stated that an indefinite supply of water can be
provided from Lake Anna or the Service Water Reservoir. Lake Anna will remain available for
any of the external hazards applicable to North Anna. The service water reservoir is a safetyrelated, seismic category I earthen structure and will also remain available for any of the
external hazards applicable to North Anna.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to deployment of
FLEX equipment – seismic hazard, if these requirements are implemented as described.
3.1.1.3 Procedural Interfaces – Seismic Hazard
NEI 12-06, Section 5.3.3 states:
There are four procedural interface considerations that should be addressed.
1. Seismic studies have shown that even seismically qualified electrical
equipment can be affected by BDB seismic events. In order to address
these considerations, each plant should compile a reference source for
the plant operators that provides approaches to obtaining necessary
instrument readings to support the implementation of the coping strategy
(see Section 3.2.1.10). This reference source should include control room
and non-control room readouts and should also provide guidance on how
and where to measure key instrument readings at containment
penetrations, where applicable, using a portable instrument (e.g., a Fluke
meter). Such a resource could be provided as an attachment to the plant
procedures/guidance. Guidance should include critical actions to perform
until alternate indications can be connected and on how to control critical
equipment without associated control power.
2. Consideration should be given to the impacts from large internal flooding
sources that are not seismically robust and do not require ac power (e.g.,
gravity drainage from lake or cooling basins for non-safety-related cooling
water systems).
3. For sites that use ac power to mitigate ground water in critical locations, a
strategy to remove this water will be required.
4. Additional guidance may be required to address the deployment of FLEX
for those plants that could be impacted by failure of a not seismically
robust downstream dam.
In the Integrated Plan the licensee does not provide any information on the availability of a
reference source for obtaining instrument readings using a portable instrument to support
coping strategy implementation. In response to the audit, the licensee stated that a FLEX
support guideline (FSG) is currently under development to provide operators with direction on
how to establish alternate monitoring and control capabilities. This is identified as Confirmatory
Item 3.1.1.3.A in Section 4.2 below.
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In the Integrated Plan, the licensee does not provide any information on non-robust internal
flooding sources that do not require ac power or the use of ac power to mitigate ground water in
critical locations. In response to the audit, the licensee stated that fire protection water piping
and other water system piping within the plant was evaluated during the Individual Plant
Examination for External Events (IPEEE) as potential seismic event induced flooding sources.
The results of this evaluation concluded that seismic-induced leakage from these systems
would not result in flooding that adversely affected safe-shutdown equipment. In addition, the
licensee stated that no subsurface dewatering pumps are required.
As described in Section 3.1.1.2 of this evaluation, the licensee’s plan does not rely on water
source that is not seismically robust.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to seismic procedural interfaces
considerations, if these requirements are implemented as described.
3.1.1.4 Considerations in Using Offsite Resources – Seismic Hazard
NEI 12-06, Section 5.3.4 states:
Severe seismic events can have far-reaching effects on the infrastructure in and
around a plant. While nuclear power plants are designed for large seismic events,
many parts of the Owner Controlled Area and surrounding infrastructure (e.g.,
roads, bridges, dams, etc.) may be designed to lesser standards. Obtaining offsite resources may require use of alternative transportation (such as air-lift
capability) that can overcome or circumvent damage to the existing local
infrastructure.
1. The FLEX strategies will need to assess the best means to obtain
resources from off-site following a seismic event.
On page 21 of the Integrated Plan, the licensee stated that the industry will establish two
Regional Response Centers (RRCs) to support utilities during BDB events. Dominion has
established contracts with the Pooled Equipment Inventory Company (PEICo) to participate in
the process for support of the RRCs as required. Each RRC will hold five sets of equipment,
four of which will be able to be fully deployed when requested, the fifth set will have equipment
in a maintenance cycle. In addition, on-site BDB equipment hose and cable end fittings are
standardized with the equipment supplied from the RRC. Equipment will be moved from an
RRC to a local Assembly Area, established by the Strategic Alliance for FLEX Emergency
Response (SAFER) team and the utility. Communications will be established between the
affected nuclear site and the SAFER team and required equipment moved to the site as
needed. First arriving equipment, as established during development of the nuclear site's
playbook, will be delivered to the site within 24 hours from the initial request. Confirmation of
the RRC local staging area, evaluation of access routes, and method of transportation to the
site is identified as Confirmatory Item 3.1.1.4.A in Section 4.2 below.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
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requirements of Order EA-12-049 will be met with respect to the use of off-site resources, if
these requirements are implemented as described.
3.1.2 Flooding.
NEI 12-06, Section 6.2 states:
The evaluation of external flood-induced challenges has three parts. The first part
is determining whether the site is susceptible to external flooding. The second
part is the characterization of the applicable external flooding threat. The third
part is the application of the flooding characterization to the protection and
deployment of FLEX strategies.
NEI 12-06, Section 6.2.1 states in part:
Susceptibility to external flooding is based on whether the site is a “dry” site, i.e.,
the plant is built above the design basis flood level (DBFL). For sites that are not
“dry”, water intrusion is prevented by barriers and there could be a potential for
those barriers to be exceeded or compromised. Such sites would include those
that are kept “dry” by permanently installed barriers, e.g., seawall, levees, etc.,
and those that install temporary barriers or rely on watertight doors to keep the
design basis flood from impacting safe shutdown equipment.
On Page 1 of the Integrated Plan, the licensee stated that a site-specific assessment for North
Anna provides the development of strategies, equipment lists, storage requirements, and
deployment procedures for the conditions and consequences of external flooding. The licensee
stated that the flood re-evaluation pursuant to the 10 CFR 50.54(f) letter of March 12, 2012 had
not been completed and therefore was not assumed in their Integrated Plan.
On page 2 of the Integrated Plan, the licensee provides information regarding the effects of
external flooding on the plant but did not provide a definitive statement as to whether the site is
determined to be a “dry site” or “wet site”. In response to the audit, the licensee stated that
North Anna is a “wet” site because the site is kept “dry” by a permanently installed dike. The
licensee stated that the design basis flood level is based on the maximum potential lake level of
267.3’ MSL resulting from a probable maximum precipitation (PMP) event over the Lake Anna
watershed causing a significant rise in lake level. Although the majority of the site grade is
above the design base flood level, the western portion of the Unit 2 turbine building is protected
by a dike to prevent flooding during the design basis flood. There is no deployment of FLEX
equipment in the area west of the Unit 2 turbine building; therefore there are no deployment
limitations due to flooding from the design basis flood.
On page 3 of the Integrated Plan, the licensee stated that the current flood analysis for Unit 3 is
applicable according to NEI 12-06. During the audit, the licensee was requested to clarify
whether all of the information regarding external flooding in the Integrated Plan is derived from
the most recent flood analysis (i.e., Unit 3 flood analysis). In response, the licensee stated that
the information in the Integrated Plan, Section A.1 regarding external flooding was based on the
current North Anna Units 1 and 2 UFSAR, not the North Anna Unit 3 COLA. However, since a
seiche event had not been addressed in the North Anna Units 1 and 2 UFSAR, a reference to
the North Anna Unit 3 COLA evaluation was used for completeness.
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Since the submittal of the Integrated Plan, Dominion has completed and submitted the Flood
Hazard Reevaluation Report (FHRR) (ADAMS Accession No. ML13318A090) for North Anna
requested by the 10 CFR 50.54(f) letter dated March 12, 2012. NRC review of this report is not
yet complete, but the licensee characterizes the results as follows. The reevaluation represents
the most current flooding analysis for North Anna Units 1 and 2. The reevaluation results were
mostly bounded by the original North Anna UFSAR site flooding vulnerabilities and
characteristics, in that the non-events such as seiche and dam failures continued to be nonevents. The maximum flood level due to elevated lake levels resulting from a PMP event over
the Lake Anna watershed exceeded the UFSAR value by 0.1 foot. This difference is
insignificant since the plant grade is nearly 4 feet above this flood level. The only significant
difference identified from the UFSAR was a local intense precipitation (LIP) event. Using
conservative drainage assumptions and current PMP rates, some areas of the site were subject
to short term flooding which required minimal protective actions. Details of the LIP event can be
obtained from Section 2.1 of the FHRR. Therefore, the most current analysis for flooding is the
FHRR for North Anna and is neither the current North Anna Units 1 and 2 UFSAR nor the North
Anna Unit 3 COLA.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to screening for
the flooding hazard, if these requirements are implemented as described.
3.1.2.1 Protection of FLEX Equipment – Flooding Hazard
NEI 12-06, Section 6.2.3.1 states:
These considerations apply to the protection of FLEX equipment from external
flood hazards:
1. The equipment should be stored in one or more of the following
configurations:
a. Stored above the flood elevation from the most recent site flood analysis.
The evaluation to determine the elevation for storage should be informed
by flood analysis applicable to the site from early site permits, combined
license applications, and/or contiguous licensed sites.
b. Stored in a structure designed to protect the equipment from the flood.
c. FLEX equipment can be stored below flood level if time is available and
plant procedures/guidance address the needed actions to relocate the
equipment. Based on the timing of the limiting flood scenario(s), the
FLEX equipment can be relocated [footnote 2 omitted] to a position that is
protected from the flood, either by barriers or by elevation, prior to the
arrival of the potentially damaging flood levels. This should also consider
the conditions on-site during the increasing flood levels and whether
movement of the FLEX equipment will be possible before potential
inundation occurs, not just the ultimate flood height.
2. Storage areas that are potentially impacted by a rapid rise of water should be
avoided.
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On page 17 of the Integrated Plan, the licensee stated that a study is in progress to determine
the design features, site location(s), and number of equipment storage facilities. The final
design for BDB equipment storage will be based on the guidance contained in NEI 12-06,
Section 11.3, Equipment Storage. Meeting the storage structure considerations of NEI 12-06,
Section 11.3 will conform to the storage structure considerations of Section 6.2.3.1 for the
flooding hazard. The licensee completed the BDB equipment storage study as documented in
the completed Open Item #6 of its six-month status report. Staff review of the results of this
study is included with Confirmatory Item 3.1.1.1.A in Section 4.2 below.
On page 29, and 56 of the Integrated Plan the licensee stated that the BDB pumps,
necessary hoses and fittings are protected from flooding while stored in the BDB
Storage Building(s) or in protected areas of the plant.
On page 64 of the Integrated Plan the licensee stated that the BDB portable diesel generators,
necessary cables and connectors will be protected from flooding while stored in either the BDB
Storage Building(s) or in flood protected areas of the plant.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to protection of FLEX equipment in a
flood hazard, if these requirements are implemented as described.
3.1.2.2 Deployment of FLEX Equipment – Flooding Hazard
NEI 12-06, Section 6.2.3.2 states:
There are a number of considerations which apply to the deployment of FLEX
equipment for external flood hazards:
1. For external floods with warning time, the plant may not be at power. In fact,
the plant may have been shut down for a considerable time and the plant
configuration could be established to optimize deployment. For example, the
portable pump could be connected, tested, and readied for use prior to the
arrival of the critical flood level. Further, protective actions can be taken to
reduce the potential for flooding impacts, including cooldown, borating the
RCS, isolating accumulators, isolating RCP [reactor coolant pump] seal leak
off, obtaining dewatering pumps, creating temporary flood barriers, etc.
These factors can be credited in considering how the baseline capability is
deployed.
2. The ability to move equipment and restock supplies may be hampered during
a flood, especially a flood with long persistence. Accommodations along
these lines may be necessary to support successful long-term FLEX
deployment.
3. Depending on plant layout, the ultimate heat sink may be one of the first
functions affected by a flooding condition. Consequently, the deployment of
the FLEX equipment should address the effects of LUHS, as well as ELAP.
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4. Portable pumps and power supplies will require fuel that would normally be
obtained from fuel oil storage tanks that could be inundated by the flood or
above ground tanks that could be damaged by the flood. Steps should be
considered to protect or provide alternate sources of fuel oil for flood
conditions. Potential flooding impacts on access and egress should also be
considered.
5. Connection points for portable equipment should be reviewed to ensure that
they remain viable for the flooded condition.
6. For plants that are limited by storm-driven flooding, such as Probable
Maximum Surge or Probable Maximum Hurricane (PMH), expected storm
conditions should be considered in evaluating the adequacy of the baseline
deployment strategies.
7. Since installed sump pumps will not be available for dewatering due to the
ELAP, plants should consider the need to provide water extraction pumps
capable of operating in an ELAP and hoses for rejecting accumulated water
for structures required for deployment of FLEX strategies.
8. Plants relying on temporary flood barriers should assure that the storage
location for barriers and related material provides reasonable assurance that
the barriers could be deployed to provide the required protection.
9. A means to move FLEX equipment should be provided that is also
reasonably protected from the event.
On page 100 of the Integrated Plan, the licensee stated that stored BDB equipment includes
tow vehicles (small tractors) equipped with front-end buckets and rear tow connections in order
to move or remove debris from the needed travel paths and to deploy equipment.
On page 7 of the Integrated Plan, the licensee stated that normal access to the ultimate heat
sink is lost, but the water inventory in the ultimate heat sink (UHS) remains available and robust
piping connecting the UHS to plant systems remains intact. The motive force for UHS flow, i.e.,
pumps, is assumed to be lost with no prospect for recovery.
On page 73 of the Integrated Plan the licensee stated that the BDB fuel carts, pumps,
necessary hoses, fittings, and containers will be protected from flooding events while stored in
the BDB Storage Building(s) or in protected areas of the plant. On page 72, the licensee details
how the fuel would be accessed from the underground diesel fuel oil storage tanks that are
protected from the flood hazard.
On pages 30, 31, 32, 35, 44, 45, 46, 57, 58, 66, 68, 74, and 76 of the Integrated Plan, the
licensee describes how each connection point is accessed and protected to ensure at least one
connection point will be available for strategy deployment.
North Anna is not limited by storm-driven flooding, such as Probable Maximum Surge or
Probable Maximum Hurricane (PMH). NEI 12-06, Section 6.2.3.2, Consideration 6 is not
applicable.
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The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to deployment of
FLEX equipment in a flood hazard, if these requirements are implemented as described.
3.1.2.3 Procedural Interfaces – Flooding Hazard
NEI 12-06, Section 6.2.3.3 states:
The following procedural interface considerations should be addressed.
1. Many sites have external flooding procedures. The actions necessary to
support the deployment considerations identified above should be
incorporated into those procedures.
2. Additional guidance may be required to address the deployment of FLEX for
flooded conditions (i.e., connection points may be different for flooded vs.
non-flooded conditions).
3. FLEX guidance should describe the deployment of temporary flood barriers
and extraction pumps necessary to support FLEX deployment.
On page 17 of the Integrated Plan, the licensee stated that FSGs will be developed in
accordance with the Pressurized Water Reactor Owners Group (PWROG) guidelines. Interface
with ECA-0.0, “Loss of All AC Power”, will be revised to the extent necessary to include
appropriate reference to FSGs. Interface with Abnormal Procedures O-AP-41, Severe Weather
Conditions, will be revised to the extent necessary to include appropriate reference to FSGs.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to procedural
interfaces in a flood hazard, if these requirements are implemented as described.
3.1.2.4 Considerations in Using Offsite Resources – Flooding Hazard
NEI 12-06, Section 6.2.3.4 states:
Extreme external floods can have regional impacts that could have a significant
impact on the transportation of off-site resources.
1. Sites should review site access routes to determine the best means to obtain
resources from off-site following a flood.
2. Sites impacted by persistent floods should consider where equipment
delivered from off-site could be staged for use on-site.
On page 21 of the Integrated Plan, the licensee stated that the industry will establish two RRCs
to support utilities during BDB events. Dominion has established contracts with the Pooled
Equipment Inventory Company (PEICo) to participate in the process for support of the RRCs as
required. Each RRC will hold five sets of equipment, four of which will be able to be fully
deployed when requested, the fifth set will have equipment in a maintenance cycle. In addition,
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on-site BDB equipment hose and cable end fittings are standardized with the equipment
supplied from the RRC. Equipment will be moved from an RRC to a local Assembly Area,
established by the SAFER team and the utility. Communications will be established between
the affected nuclear site and the SAFER team and required equipment moved to the site as
needed. First arriving equipment, as established during development of the nuclear site's
playbook, will be delivered to the site within 24 hours from the initial request. Confirmation of
the RRC local staging area, evaluation of access routes, and method of transportation to the
site is combined with Confirmatory Item 3.1.1.4.A in Section 4.2 below.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to the use of off-site resources, if
these requirements are implemented as described.
3.1.3 High Winds
NEI 12-06, Section 7, provides the NRC-endorsed screening process for evaluation of high wind
hazards. This screening process considers the hazard due to hurricanes and tornadoes. The
first part of the evaluation of high wind challenges is determining whether the site is potentially
susceptible to different high wind conditions to allow characterization of the applicable high wind
hazard.
The screening for high wind hazards associated with hurricanes should be accomplished by
comparing the site location to NEI 12-06, Figure 7-1 (Figure 3-1 of U.S. NRC, “Technical Basis
for Regulatory Guidance on Design Basis Hurricane Wind Speeds for Nuclear Power Plants,”
NUREG/CR-7005, December, 2009); if the resulting frequency of recurrence of hurricanes with
wind speeds in excess of 130 mph exceeds 10-6 per year, the site should address hazards due
to extreme high winds associated with hurricanes.
The screening for high wind hazard associated with tornadoes should be accomplished by
comparing the site location to NEI 12-06, Figure 7-2, from U.S. NRC, “Tornado Climatology of
the Contiguous United States,” NUREG/CR-4461, Rev. 2, February 2007; if the recommended
tornado design wind speed for a 10-6/year probability exceeds 130 mph, the site should address
hazards due to extreme high winds associated with tornadoes.
On page 1 of the Integrated Plan, the licensee stated that a site-specific assessment of North
Anna provides for the development of strategies, equipment lists, storage requirements, and
deployment procedures for the conditions and consequences of storms such as hurricanes, high
winds, and tornados.
On page 3 of the Integrated Plan, the licensee stated that the plant design bases address the
storm hazards of hurricanes, high winds and tornadoes. With the site being approximately 100
miles from the Atlantic Ocean, hurricanes and tropical storms tend to weaken before reaching
the site. For extreme straight winds, the extreme 1-mile wind speed is defined as the 1-mile
passage of wind with the highest speed for the day. The extreme 1-mile wind speed at 30 feet
above the ground, which is predicted to occur once in 100 years, is 80 mph. The tornado model
used for design purposes has a 300 mph rotational velocity and a 60 mph translational velocity.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
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assurance that the requirements of Order EA-12-049 will be met with respect to screening for
severe storms with high winds, if these requirements are implemented as described.
3.1.3.1 Protection of FLEX Equipment - High Winds Hazard
NEI 12-06, Section 7.3.1 states:
These considerations apply to the protection of FLEX equipment from high wind
hazards:
1. For plants exposed to high wind hazards, FLEX equipment should be stored
in one of the following configurations:
a. In a structure that meets the plant’s design basis for high wind hazards
(e.g., existing safety-related structure).
b. In storage locations designed to or evaluated equivalent to ASCE 7-10,
Minimum Design Loads for Buildings and Other Structures given the
limiting tornado wind speeds from Regulatory Guide 1.76 or design basis
hurricane wind speeds for the site.
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
Given the FLEX basis limiting tornado or hurricane wind speeds,
building loads would be computed in accordance with requirements of
ASCE 7-10. Acceptance criteria would be based on building
serviceability requirements not strict compliance with stress or
capacity limits. This would allow for some minor plastic deformation,
yet assure that the building would remain functional.

Tornado missiles and hurricane missiles will be accounted for in that
the FLEX equipment will be stored in diverse locations to provide
reasonable assurance that N sets of FLEX equipment will remain
deployable following the high wind event. This will consider locations
adjacent to existing robust structures or in lower sections of buildings
that minimizes the probability that missiles will damage all mitigation
equipment required from a single event by protection from adjacent
buildings and limiting pathways for missiles to damage equipment.

The axis of separation should consider the predominant path of
tornados in the geographical location. In general, tornadoes travel
from the West or West Southwesterly direction, diverse locations
should be aligned in the North-South arrangement, where possible.
Additionally, in selecting diverse FLEX storage locations,
consideration should be given to the location of the diesel generators
and switchyard such that the path of a single tornado would not impact
all locations.

Stored mitigation equipment exposed to the wind should be
adequately tied down. Loose equipment should be in protective
boxes that are adequately tied down to foundations or slabs to prevent
protected equipment from being damaged or becoming airborne.
(During a tornado, high winds may blow away metal siding and metal
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deck roof, subjecting the equipment to high wind forces.)
c. In evaluated storage locations separated by a sufficient distance that
minimizes the probability that a single event would damage all FLEX
mitigation equipment such that at least N sets of FLEX equipment would
remain deployable following the high wind event. (This option is not
applicable for hurricane conditions).

Consistent with configuration b., the axis of separation should consider
the predominant path of tornados in the geographical location.

Consistent with configuration b., stored mitigation equipment should
be adequately tied down.
On page 17 of the Integrated Plan, the licensee stated that a study is in progress to determine
the design features, site location(s), and number of equipment storage facilities. The final
design for BDB equipment storage will be based on the guidance contained in NEI 12-06,
Section 11.3, Equipment Storage. A future submittal will be provided with the results of the
equipment storage study. The licensee’s plans to follow the storage structure considerations of
NEI 12-06, Section 11.3, will conform to the storage structure considerations of Section 7.3.1 for
the high wind hazard. The licensee completed the BDB equipment storage study as
documented in the completed Open Item #6 of its six-month status report. Staff review of the
results of this study is included with Confirmatory Item 3.1.1.1.A in Section 4.2 below.
On page 29, and 57 of the Integrated Plan the licensee stated that the BDB pumps,
necessary hoses and fittings are protected from severe storms with high winds while
stored in the BDB Storage Building(s) or in protected areas of the plant.
On page 65 of the Integrated Plan the licensee stated that the BDB portable diesel generators,
necessary cables and connectors will be protected from severe storms with high winds while
stored in either the BDB Storage Building(s) or in wind/missile protected areas of the plant.
The Integrated Plan stated that the BDB pumps, necessary hoses and fittings, BDB portable
diesel generators, and necessary cables and connectors are protected from severe storms with
high winds while stored in the BDB Storage Building(s) or in protected areas of the plant.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to protection of FLEX equipment in a
high wind hazard, if these requirements are implemented as described.
3.1.3.2 Deployment of FLEX Equipment - High Winds Hazard
NEI 12-06, Section 7.3.2 states:
There are a number of considerations which apply to the deployment of FLEX
equipment for high wind hazards:
1. For hurricane plants, the plant may not be at power prior to the simultaneous
ELAP and LUHS condition.
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In fact, the plant may have been shut down and
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the plant configuration could be established to optimize FLEX deployment.
For example, the portable pumps could be connected, tested, and readied for
use prior to the arrival of the hurricane. Further, protective actions can be
taken to reduce the potential for wind impacts. These factors can be
credited in considering how the baseline capability is deployed.
2. The ultimate heat sink may be one of the first functions affected by a
hurricane due to debris and storm surge considerations. Consequently, the
evaluation should address the effects of ELAP/LUHS, along with any other
equipment that would be damaged by the postulated storm.
3. Deployment of FLEX following a hurricane or tornado may involve the need to
remove debris. Consequently, the capability to remove debris caused by
these extreme wind storms should be included.
4. A means to move FLEX equipment should be provided that is also reasonably
protected from the event.
5. The ability to move equipment and restock supplies may be hampered during
a hurricane and should be considered in plans for deployment of FLEX
equipment.
On page 100 of the Integrated Plan, the licensee stated that preferred travel pathways will be
determined using the guidance contained in NEI 12-06. The pathways will attempt to avoid
areas with trees, power lines, and other potential obstructions. Debris removal equipment will
be kept in the BDB Storage Building(s) so that it is protected from the severe storm. The stored
BDB equipment includes tow vehicles (small tractors) equipped with front-end buckets and rear
tow connections in order to move or remove debris from the needed travel paths. A front-end
loader will also be available to deal with more significant debris conditions.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to deployment of
FLEX equipment in a high wind hazard, if these requirements are implemented as described.
3.1.3.3 Procedural Interfaces - High Winds Hazard
NEI 12-06, Section 7.3.3, states:
The overall plant response strategy should be enveloped by the baseline
capabilities, but procedural interfaces may need to be considered. For example,
many sites have hurricane procedures. The actions necessary to support the
deployment considerations identified above should be incorporated into those
procedures.
On page 17 of the Integrated Plan, the licensee stated that FSGs will be developed in
accordance with PWROG guidelines. Interface with ECA-0.0, will be revised to the extent
necessary to include appropriate reference to FSGs. Interface with Abnormal Procedures OAP-41, Severe Weather Conditions, will be revised to the extent necessary to include
appropriate reference to FSGs.
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The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to procedural
interfaces in a high wind hazard, if these requirements are implemented as described.
3.1.3.4 Considerations in Using Offsite Resources – High Winds Hazard
NEI 12-06, Section 7.3.4 states:
Extreme storms with high winds can have regional impacts that could have a
significant impact on the transportation of off-site resources.
1. Sites should review site access routes to determine the best means to obtain
resources from off-site following a hurricane.
2. Sites impacted by storms with high winds should consider where equipment
delivered from off-site could be staged for use on-site.
On page 21 of the Integrated Plan, the licensee stated that the industry will establish two RRCs
to support utilities during BDB events. Dominion has established contracts with the Pooled
Equipment Inventory Company (PEICo) to participate in the process for support of the RRCs as
required. Each RRC will hold five sets of equipment, four of which will be able to be fully
deployed when requested, the fifth set will have equipment in a maintenance cycle. In addition,
on-site BDB equipment hose and cable end fittings are standardized with the equipment
supplied from the RRC. Equipment will be moved from an RRC to a local Assembly Area,
established by the SAFER team and the utility. Communications will be established between
the affected nuclear site and the SAFER team and required equipment moved to the site as
needed. First arriving equipment, as established during development of the nuclear site's
playbook, will be delivered to the site within 24 hours from the initial request. Confirmation of
the RRC local staging area, evaluation of access routes, and method of transportation to the
site is combined with Confirmatory Item 3.1.1.4.A in Section 4.2 below.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to the use of off-site resources, if
these requirements are implemented as described.
3.1.4 Snow, Ice and Extreme Cold
As discussed in part in NEI 12-06, Section 8.2.1:
All sites should consider the temperature ranges and weather conditions for their site in storing
and deploying their FLEX equipment consistent with normal design practices. All sites outside
of Southern California, Arizona, the Gulf Coast and Florida are expected to address deployment
for conditions of snow, ice, and extreme cold. All sites located North of the 35th Parallel should
provide the capability to address extreme snowfall with snow removal equipment. Finally, all
sites except for those within Level 1 and 2 of the maximum ice storm severity map contained in
Figure 8-2 should address the impact of ice storms.
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On page 1 of the Integrated Plan, the licensee stated that a site-specific assessment for North
Anna provides for the development of strategies, equipment lists, storage requirements, and
deployment procedures for the conditions and consequences of snow and ice storms, and cold.
On page 4 of the Integrated Plan, the licensee stated that snowfalls of 4 inches or more occur,
on average, once a year, and snow usually only remains on the ground from 1 to 4 days at a
time. Richmond averages about 14.6 inches of snow a year. The North Anna UFSAR stated
that an examination of the period between 1977 and 1987 indicates that there were only six
documented cases of ice storms in Louisa County and the immediately surrounding counties.
Of these, two were reported to have caused serious damage (including damage to power lines
and trees).
The licensee further stated that temperatures in the site region rarely fall below 10 degrees F.
The lowest temperature recorded in Richmond was minus 12 degrees F in January 1940 and
the lowest recorded in Charlottesville was minus 9 degrees F in January 1985. Such low
temperatures could adversely affect access to and the flow path from Lake Anna or the Service
Water Reservoir. Ice could form on the surface of Lake Anna or the Service Water Reservoir
and impact the FLEX strategy. However, the licensee stated that capabilities are available to
break through the ice, if needed, to provide access and a flow path.
During the audit, the licensee was asked to provide a discussion on the applicability of the data
used to determine the applicable snow, ice, and extreme cold hazards, in relation to the
protection and deployment of FLEX equipment, given the time period of the data. In response,
the licensee stated that the high and low temperature data stated in the OIP have been
confirmed to be accurate based on published data for the southeast region of the Unite States
through 2012.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to screening for
snow, ice, and extreme cold hazards, if these requirements are implemented as described.
3.1.4.1 Protection of FLEX Equipment - Snow, Ice and Extreme Cold Hazard
NEI 12-06, Section 8.3.1 states:
These considerations apply to the protection of FLEX equipment from snow, ice,
and extreme cold hazards:
1. For sites subject to significant snowfall and ice storms, portable FLEX
equipment should be stored in one of the two configurations.
a. In a structure that meets the plant’s design basis for the snow, ice and
cold conditions (e.g., existing safety-related structure).
b. In a structure designed to or evaluated equivalent to ASCE 7-10,
Minimum Design Loads for Buildings and Other Structures for the snow,
ice, and cold conditions from the site’s design basis.
c. Provided the N sets of equipment are located as described in a. or b.
above, the N+1 equipment may be stored in an evaluated storage
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location capable of withstanding historical extreme weather conditions
such that the equipment is deployable.
2. Storage of FLEX equipment should account for the fact that the equipment will
need to function in a timely manner. The equipment should be maintained at
a temperature within a range to ensure its likely function when called upon.
For example, by storage in a heated enclosure or by direct heating (e.g.,
jacket water, battery, engine block heater, etc.).
On page 17 of the Integrated Plan, the licensee stated that a study is in progress to determine
the design features, site location(s), and number of equipment storage facilities. The final
design for BDB equipment storage will be based on the guidance contained in NEI 12-06,
Section 11.3, Equipment Storage. The storage structure considerations of NEI 12-06, Section
11.3 conform to the storage structure considerations of Section 8.3.1 for the snow, ice and
extreme cold hazard. The licensee completed the BDB equipment storage study as
documented in the completed Open Item #6 of its six-month status report. Staff review of the
results of this study is included with Confirmatory Item 3.1.1.1.A in Section 4.2 below.
On pages 29 and 57 of the Integrated Plan, the licensee stated that the BDB pumps, necessary
hoses and fittings, are protected from snow, ice, and extreme cold while stored in the BDB
Storage Building or in protected areas of the plant to ensure equipment readiness at extreme
temperatures when called upon.
On page 65 of the Integrated Plan, the licensee stated that the BDB portable diesel generators,
necessary cables and connectors will be protected from snow, ice and extreme cold events
while stored in either the BDB Storage Building(s) or in weather protected areas of the plant to
ensure equipment readiness at extreme temperatures when called upon.
On page 92 of the Integrated Plan, the licensee stated that the FLEX strategies for maintenance
and/or support of safety functions involve several elements. One element is to ensure that
heating is adequate to maintain acceptable environmental conditions for equipment operation.
The licensee stated that details of the ventilation strategy are under development and will
conform to the guidance given in NEI 12-06.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to protection of FLEX equipment in a
snow, ice, and extreme cold hazard, if these requirements are implemented as described.
3.1.4.2 Deployment of Portable Equipment - Snow, Ice and Extreme Cold Hazard
NEI 12-06, Section 8.3.2 states:
There are a number of considerations that apply to the deployment of FLEX
equipment for snow, ice, and extreme cold hazards:
1. The FLEX equipment should be procured to function in the extreme
conditions applicable to the site. Normal safety-related design limits for
outside conditions may be used, but consideration should also be made for
any manual operations required by plant personnel in such conditions.
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2. For sites exposed to extreme snowfall and ice storms, provisions should be
made for snow/ice removal, as needed to obtain and transport FLEX
equipment from storage to its location for deployment.
3. For some sites, the ultimate heat sink and flow path may be affected by
extreme low temperatures due to ice blockage or formation of frazil ice.
Consequently, the evaluation should address the effects of such a loss of
UHS on the deployment of FLEX equipment. For example, if UHS water is to
be used as a makeup source, some additional measures may need to be
taken to assure that the FLEX equipment can utilize the water.
On pages 16 and 17 of the Integrated Plan, the licensee stated that design requirements and
supporting analysis will be developed for portable equipment that directly performs a FLEX
mitigation strategy for core cooling, RCS inventory, containment function, and SFP cooling. The
design requirements and supporting analysis provide the inputs, assumptions, and documented
analysis that the mitigation strategy and support equipment will perform as intended.
Manufacturer's information is used in establishing the basis for the equipment use. The
specified portable equipment capacities ensure that the strategy can be effective over a range
of plant and environmental conditions. This design documentation will be auditable, consistent
with generally accepted engineering principles and practices, and controlled within Dominion's
document management system. The basis for designed flow requirements considers the
following factors: Potential clogging of strainers, pumps, valves or hoses from debris or ice
when using Lake Anna, the service water reservoir, or the discharge canal as a water supply;
and environmental conditions (e.g., extreme high and low temperature range) in which the
equipment would be expected to operate.
On page 101 of the Integrated Plan, the licensee stated that the BDB equipment for removing
debris (tractors and front-end loader) will be protected from snow, ice and extreme cold events
while stored in BDB Storage Building(s) to ensure equipment readiness at extreme
temperatures when called upon.
On page 4 of the Integrated Plan, the licensee stated that, low temperatures could adversely
affect access to and the flow path from Lake Anna or the service water reservoir. Ice could form
on the surface of Lake Anna or the service water reservoir and impact the FLEX strategy. The
licensee stated that capabilities are available to break through the ice, if needed, to provide
access and a flow path.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01 and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to deployment of
FLEX equipment in snow, ice, and extreme cold hazard, if these requirements are implemented
as described.
3.1.4.3 Procedural Interfaces - Snow, Ice and Extreme Cold Hazard
NEI 12-06, Section 8.3.3 states:
The only procedural enhancements that would be expected to apply involve
addressing the effects of snow and ice on transport the FLEX equipment. This
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includes both access to the transport path, e.g., snow removal, and appropriately
equipped vehicles for moving the equipment.
On page 17 of the Integrated Plan, the licensee stated that FSGs will be developed in
accordance with PWROG guidelines. Interface with ECA-0.0 will be revised to the extent
necessary to include appropriate reference to FSGs. Interface with Abnormal Procedures OAP-41, Severe Weather Conditions, will be revised to the extent necessary to include
appropriate reference to FSGs.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to procedural
interfaces for snow, ice, and extreme cold hazard, if these requirements are implemented as
described.
3.1.4.4 Considerations in Using Offsite Resources - Snow, Ice and Extreme Cold Hazard
NEI 12-06, Section 8.3.4, states:
Severe snow and ice storms can affect site access and can impact staging areas
for receipt of off-site materials and equipment.
On page 21 of the Integrated Plan, the licensee stated that the industry will establish two RRCs
to support utilities during BDB events. Dominion has established contracts with the Pooled
Equipment Inventory Company (PEICo) to participate in the process for support of the RRCs as
required. Each RRC will hold five sets of equipment, four of which will be able to be fully
deployed when requested, the fifth set will have equipment in a maintenance cycle. In addition,
on-site BDB equipment hose and cable end fittings are standardized with the equipment
supplied from the RRC. Equipment will be moved from an RRC to a local Assembly Area,
established by the SAFER team and the utility. Communications will be established between
the affected nuclear site and the SAFER team and required equipment moved to the site as
needed. First arriving equipment, as established during development of the nuclear site's
playbook, will be delivered to the site within 24 hours from the initial request. Confirmation of
the RRC local staging area, evaluation of access routes, and method of transportation to the
site is combined with Confirmatory Item 3.1.1.4.A in Section 4.2 below.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to the use of off-site resources, if
these requirements are implemented as described.
3.1.5 High Temperatures
NEI 12-06, Section 9.2 states:
All sites will address high temperatures. Virtually every state in the lower 48
contiguous United States has experienced temperatures in excess of 110˚F.
Many states have experienced temperatures in excess of 120˚F.
In this case, sites should consider the impacts of these conditions on deployment
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of the FLEX equipment.
On page 1 of the Integrated Plan, the licensee stated that that a site-specific assessment for
North Anna provides for the development of strategies, equipment lists, storage requirements,
and deployment procedures for the conditions and consequences of extreme heat.
On page 4 of the Integrated Plan, the licensee stated that temperatures in the site region rarely
exceed 95 degrees F (UFSAR Section 2.3.1). The peak temperature recorded in Richmond
was 105 degrees F in July 1977 and the peak temperature recorded in Charlottesville was 107
degrees F in September 1954 (UFSAR Table 2.3-2).
During the audit, the licensee was asked to provide a discussion on the applicability of the data
used to determine the applicable high temperature hazard, in relation to the protection and
deployment of FLEX equipment, given the time period of the data. In response, the licensee
stated that the high temperature data stated in the Integrated Plan has been confirmed to be
accurate based on published data for the southeast region of the Unite States through 2012.
However the licensee did not state whether they intend to use 107 degrees F or the values
recommended in NEI 12-06 Section 9.2 as the basis for protection and deployment strategies of
FLEX equipment. This is identified as Confirmatory Item 3.1.5 in Section 4.2 below.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to screening for the high temperature
hazard, if these requirements are implemented as described.
3.1.5.1 Protection of FLEX Equipment - High Temperature Hazard
NEI 12-06, Section 9.3.1, states:
The equipment should be maintained at a temperature within a range to ensure
its likely function when called upon.
On pages 29 and 57 of the Integrated Plan, the licensee stated that the BDB pumps, necessary
hoses and fittings, are protected from high temperature events while stored in the BDB Storage
Building or in protected areas of the plant to ensure equipment readiness at extreme
temperatures when called upon.
On page 65 of the Integrated Plan, the licensee stated that the BDB portable diesel generators,
necessary cables and connectors will be protected from high temperature events while stored in
either the BDB Storage Building(s) or in weather protected areas of the plant to ensure
equipment readiness at extreme temperatures when called upon.
On page 92 of the Integrated Plan, the licensee stated that the FLEX strategies for maintenance
and/or support of safety functions involve several elements. One element is to ensure that
cooling is adequate to maintain acceptable environmental conditions for equipment operation.
The licensee stated that the details of the ventilation strategy are under development and will
conform to the guidance given in NEI 12-06.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
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assurance that the requirements of Order EA-12-049 will be met with respect to the protection of
FLEX equipment in a high temperature hazard, if these requirements are implemented as
described.
3.1.5.2 Deployment of FLEX Equipment - High Temperature Hazard
NEI 12-06, Section 9.3.2 states:
The FLEX equipment should be procured to function, including the need to move
the equipment, in the extreme conditions applicable to the site. The potential
impact of high temperatures on the storage of equipment should also be
considered, e.g., expansion of sheet metal, swollen door seals, etc. Normal
safety-related design limits for outside conditions may be used, but consideration
should also be made for any manual operations required by plant personnel in
such conditions.
On pages 16 and 17 of the Integrated Plan, the licensee stated that design requirements and
supporting analysis will be developed for portable equipment that directly performs a FLEX
mitigation strategy for core cooling, RCS inventory, containment function, and SFP cooling. The
design requirements and supporting analysis provide the inputs, assumptions, and documented
analysis that the mitigation strategy and support equipment will perform as intended.
Manufacturer's information is used in establishing the basis for the equipment use. The
specified portable equipment capacities ensure that the strategy can be effective over a range
of plant and environmental conditions. This design documentation will be auditable, consistent
with generally accepted engineering principles and practices, and controlled within Dominion's
document management system. The basis for designed flow requirements considers
environmental conditions (e.g., extreme high and low temperature range) in which the
equipment would be expected to operate.
In the Integrated Plan, the licensee did not address considerations for any manual actions
required by plant personnel in high temperature conditions. This has been identified as
Confirmatory Item 3.1.5.2.A in Section 4.2 below.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to deployment of FLEX equipment in
a high temperature hazard, if these requirements are implemented as described.
3.1.5.3 Procedural Interfaces – High Temperature Hazard
NEI 12-06, Section 9.3.3 states:
The only procedural enhancements that would be expected to apply involve
addressing the effects of high temperatures on the FLEX equipment.
The licensee’s approach to addressing the effects of high temperatures on the FLEX equipment
is discussed in 3.1.5.2 of this evaluation. Staff review of inclusion of any manual actions from
above or other procedural enhancements will be included with Confirmatory Action 3.1.5.2.A.
The licensee’s approach described above, as currently understood, is consistent with the
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guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to the procedural
interfaces – high temperature hazard, if these requirements are implemented as described.
3.2
PHASED APPROACH
Attachment (2) to Order EA-12-049 describes the three-phase approach required for mitigating
BDBEEs in order to maintain or restore core cooling, containment and spent fuel pool cooling
capabilities. The phases consist of an initial phase using installed equipment and resources,
followed by a transition phase using portable onsite equipment and consumables and a final
phase using offsite resources.
To meet these EA-12-049 requirements, licensees will establish a baseline coping capability to
prevent fuel damage in the reactor core or SFP and to maintain containment capabilities in the
context of a BDBEE that results in the loss of all ac power, with the exception of buses supplied
by safety-related batteries through inverters, and loss of normal access to the UHS.
As discussed in NEI 12-06, Section 1.3, plant specific analysis will determine the duration of
each phase.
3.2.1
RCS Cooling and Heat Removal, and RCS Inventory Control Strategies
NEI 12-06, Table 3-2 and Appendix D summarize one acceptable approach for reactor core
cooling & heat removal, and RCS inventory control strategies. This approach uses the installed
auxiliary feedwater (AFW) system to provide steam generator (SG) makeup sufficient to
maintain or restore SG level in order to continue to provide core cooling for the initial phase.
This approach relies on depressurization of the SGs for makeup with a portable injection source
in order to provide core cooling for the transition and final phases. This approach accomplishes
reactor coolant system (RCS) inventory control and maintenance of long term subcriticality
through the use of low leak reactor coolant pump seals and/or borated high pressure RCS
makeup with a letdown path.
As described in NEI 12-06, Section 3.2.1.7 and JLD-ISG-2012-01, Section 2.1, strategies that
have a time constraint to be successful should be identified and a basis provided that the time
can be reasonably met. NEI 12-06, Section 3 provides the performance attributes, general
criteria, and baseline assumptions to be used in developing the technical basis for the time
constraints. Since the event is a beyond-design-basis event, the analysis used to provide the
technical basis for time constraints for the mitigation strategies may use nominal initial values
(without uncertainties) for plant parameters, and best-estimate physics data. All equipment
used for consequence mitigation may assume to operate at nominal setpoints and capacities.
NEI 12-06, Section 3.2.1.2 describes the initial plant conditions for the at-power mode of
operation; Section 3.2.1.3 describes the initial conditions; and Section 3.2.1.4 describes
boundary conditions for the reactor transient.
Acceptance criteria for the analyses serving as the technical basis for establishing the time
constraints for the baseline coping capabilities described in NEI 12-06, which provide an
acceptable approach, as endorsed by JLD-ISG-2012-01, to meeting the requirements of EA-12049 for maintaining core cooling are 1) the preclusion of core damage as discussed in NEI 1206, Section 1.3 as the purpose of FLEX; and 2) prevention of recriticality as discussed in
Appendix D, Table D-1.
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During the audit, the licensee was requested to specify which analysis performed in WCAP17601 is being applied to North Anna. Additionally, the licensee was requested to justify the
use of that analysis by identifying and evaluating the important parameters and assumptions
demonstrating that they are representative of North Anna and appropriate for simulating the
ELAP transient.
In response to the audit, the licensee stated that the analysis applicable to North Anna is
presented in Section 5.2.1 of WCAP-17601. The applicability of this reference case to North
Anna is evaluated in detail in ETE-NAF-2012-0150, Section 6.3. The staff’s assessment of the
licensee’s computer codes and analysis is presented in the following section.
3.2.1.1
Computer Code Used for the ELAP Analysis
NEI 12-06, Section 1.3 states:
To the extent practical, generic thermal hydraulic analyses will be developed to
support plant- specific decision-making. Justification for the duration of each
phase will address the on-site availability of equipment, the resources necessary
to deploy the equipment consistent with the required timeline, anticipated site
conditions following the beyond-design-basis external event, and the ability of the
local infrastructure to enable delivery of equipment and resources from offsite.
The licensee provided a Sequence of Events (SOE) in its integrated plan, which included the
time constraints and the technical basis for the site. To support the mitigating strategy in its
integrated plan, the licensee has elected to reference generic ELAP analysis performed with the
NOTRUMP computer code. Although NOTRUMP has been reviewed and approved for
performing small-break loss of coolant accident (LOCA) analysis for PWRs, the NRC staff had
not previously examined its technical adequacy for simulating an ELAP event. In particular, the
ELAP scenario is differentiated from typical design-basis small-break LOCA scenarios in several
key respects, including the absence of normal emergency core cooling system (ECCS) injection
and the substantially reduced leakage rate, which places significantly greater emphasis on the
accurate prediction of primary-to-secondary heat transfer, natural circulation, and two-phase
flow within the RCS. As a result of these differences, concern arose associated with the use of
the NOTRUMP code for ELAP analysis for modeling of two-phase flow within the RCS and heat
transfer across the steam generator tubes as single-phase natural circulation transitions to twophase flow and the reflux condensation cooling mode.
During the audit, the licensee clarified that the SOE was based specifically on the generic
NOTRUMP analysis in Section 5.2.1 of WCAP-17601-P that considers a four-loop
Westinghouse plant with standard reactor coolant pump seals. The analysis assumes 21 gpm
leakage per reactor coolant pump plus 1 gpm unidentified leakage. Two hours following event
initiation, the plant is assumed to be cooled down symmetrically at a rate of approximately 70 °F
per hour to a final steam generator pressure of 300 psia.
During the audit, the licensee was requested to clarify whether the 33-hour timeframe discussed
in the submittal as the timeframe for providing RCS makeup is based on the first or the last RCS
loop in the generic NOTRUMP analysis in Section 5.2.1 of WCAP-17601-P entering reflux
cooling. If the 33-hour timeframe were based on the last loop entering reflux cooling, the
licensee was further requested to identify the times at which the other RCS loops entered reflux
cooling and justify that they would not have accumulated unacceptable quantities of condensed,
deborated water in the loop seals.
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In response to this audit question, the licensee stated that the onset of reflux cooling occurs at
approximately the same time in all loops in the NOTRUMP calculation. The licensee stated that
the PWROG is developing a revision to the criterion for determining the entry into reflux cooling.
The revised criterion will be documented in WCAP-17792, which is scheduled to be issued by
the end of 2013. The licensee stated that, if the timeframe for entering reflux cooling
documented in WCAP-17792 is changed from 33 hours, an update will be provided in the
February 2014 six-month update submittal.
Section 5.3.1 of WCAP-17601-P discusses the extension of the generic four-loop analysis in
Section 5.2.1 to Westinghouse plants of other designs, including the three-loop NSSS design
applicable to the reactors at North Anna. Section 5.3.1 of WCAP-17601-P concludes that the
results are applicable or bounding relative to the entire Westinghouse fleet. However, the staff
noted that this conclusion is based upon using the timing of core uncovery as a figure of merit;
whereas, due to issues discussed above regarding the modeling of reflux condensation cooling,
the staff’s current position is that primary makeup should be provided prior to entering the reflux
condensation cooling mode. The licensee’s integrated plan submittal had used a time
constraint of 33 hours for providing makeup to the RCS. This time was based on the time of
entry into reflux cooling as defined by the authors of WCAP-17601-P for the analysis in Section
5.2.1. The definitions and rationale underlying the selection of 33 hours as the time of entry into
the reflux condensation cooling mode have not been adequately justified to the staff. In an
attempt to provide margin to the 33-hour time constraint derived from WCAP-17601-P, the
licensee’s six-month update stated that reactor coolant system makeup will actually be provided
by 16 hours instead of by 33 hours. However, at the current time, adequate basis has not been
presented to justify that 16 hours is an appropriate time constraint for preventing entry into the
reflux cooling mode. Because the PWROG (and hence the licensee) has not finalized the
criterion for determining the entry into reflux condensation cooling, a final determination cannot
be made at this time as to (1) whether the generic analysis in Section 5.2.1 of WCAP-17601-P
is bounding relative to North Anna with respect to the time of predicted entry into reflux cooling
and (2) whether providing makeup by 16 hours is sufficient to avoid entry into the reflux
condensation cooling mode.
Although North Anna’s integrated plan is based on an analysis that considers leakage from
standard RCP seals, the licensee stated that Flowserve N-9000 low-leakage RCP seals with the
Abeyance feature will eventually be installed at North Anna on all RCPs. However, only two of
three RCPs at each unit will have the seals installed by the FLEX implementation date. The
licensee stated that with essentially zero leakage from the two Flowserve N-9000 seals with the
Abeyance feature, the duration of natural circulation within the RCS would be significantly
extended, allowing additional time for deployment of the BDB RCS injection pump. The staff
expects the installation of the Flowserve N-9000 seals with the Abeyance feature will provide
North Anna significant margin relative to the analysis in Section 5.2.1 of WCAP-17601-P;
however, the low-leakage performance of these seals with the Abeyance feature under
extended station blackout conditions has not yet been adequately demonstrated to the NRC
staff.
Therefore, in light of the above discussion regarding codes and analysis, the staff has
designated the following Confirmatory Items:
Reliance on the NOTRUMP code for the ELAP analysis of Westinghouse plants is
limited to the flow conditions before reflux condensation initiates. This includes
specifying an acceptable definition for reflux condensation cooling. This is identified as
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Confirmatory Item 3.2.1.1.A in Section 4.2 below.
Confirmation that the generic analysis in Section 5.2.1 of WCAP-17601-P is applicable
or bounding with respect to North Anna for an appropriate figure of merit for defining
entry into the reflux condensation cooling mode. This is identified as Confirmatory Item
3.2.1.1.B in Section 4.2 below.
The analysis in WCAP-17601-P that the licensee has relied upon, as further elaborated in the
PWROG’s accompanying core cooling position paper, attempts to prevent intrusion of nitrogen
gas from the cold leg accumulators into the reactor coolant system by terminating the RCS
depressurization at a SG pressure that is sufficient to preclude gas injection. During the audit
the licensee was requested to discuss the analytical methodology and key assumptions for
assessing the potential for nitrogen injection from accumulators during an ELAP event. The
licensee was further requested to identify any instrumentation operators would rely upon to
ensure that nitrogen injection will not occur.
In response to the audit question, the licensee stated that the North Anna ELAP response is
consistent with the PWROG’s core cooling position paper with respect to the methodology for
preventing nitrogen injection from accumulators during an ELAP event.
The licensee stated that SG pressure is the indication monitored to ensure nitrogen injection
does not occur during the ELAP. The licensee stated that current setpoints in ECA-0.0, which is
the emergency contingency action procedure for a loss of all alternating current power, are
sufficient to preclude nitrogen injection. Specifically, the licensee stated that the setpoint used
in ECA-0.0 for minimum SG pressure was revised in March 2008, to reflect a revision to the
assumed expansion of the nitrogen gas in the accumulators from an adiabatic process to an
isothermal process. The licensee indicated that, if the nitrogen temperature remains constant
during the expansion, as with an uninsulated accumulator during a slow-moving event such as
an ELAP, the process can be considered isothermal. On the other hand, rapid expansion of
accumulator nitrogen during a large-break LOCA may be better approximated as adiabatic. The
licensee stated that, in order to ensure that injection of nitrogen into the RCS does not adversely
affect natural circulation heat removal for core cooling, it is appropriate to base the setpoint for
minimum SG pressure on an isothermal gas expansion. The staff considers this choice to be
the appropriate one for determining nitrogen injection into the RCS in light of the physical
behavior expected during an ELAP event. The licensee stated that, to provide an allowance for
operator response and overshoot, containment heatup, SG instrument uncertainty, and variation
in primary-to-secondary differential pressure, a 100 psi margin was added to the calculated
minimum SG pressure setpoint. The licensee added that a cooldown and depressurization
beyond the current setpoints would require either (1) additional evaluations to demonstrate that
nitrogen injection cannot occur for these conditions, (2) venting of the nitrogen cover gas from
each cold leg accumulator, or (3) isolation of the cold leg accumulators from the RCS.
Based upon the staff’s review of the example calculation in Attachment 1 to the PWROG’s core
cooling position paper, it appeared possible that the imposition of a 100-psi margin could result
in the need for terminating the plant cooldown at a pressure that exceeds the pressure assumed
in the baseline analysis referenced by North Anna in Section 5.2.1 of WCAP-17601-P. A
discrepancy of this sort would be of concern, since its reconciliation implies either a reduced
margin to nitrogen injection from the accumulators or an increased final system pressure with
increased leakage from the reactor coolant system relative to the analysis in Section 5.2.1 of
WCAP-17601-P. However, the parameters in the example calculation in Attachment 1 to the
core cooling position paper were not fully representative of North Anna. Considering
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parameters expected to be more applicable to North Anna, an approximate hand calculation
performed by the staff suggests that the inclusion of a 100-psi margin into the calculation for
preventing nitrogen injection for North Anna may be consistent with the depressurization
terminus assumed in WCAP-17601-P. Ultimately, however, this determination is the licensee’s
responsibility, and sufficient basis was not provided in the licensee’s response to confirm the
consistency of the margin imposed to prevent accumulator nitrogen injection with the cooldown
terminus assumed in WCAP-17601-P. This is identified as Confirmatory Item 3.2.1.1.C in
Section 4.2 below.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory Items, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to the computer code used for the
ELAP analysis, if these requirements are implemented as described.
3.2.1.2 Reactor Coolant Pump Seal Leakage Rates
NEI 12-06, Section 1.3 states:
To the extent practical, generic thermal hydraulic analyses will be developed to
support plant specific decision-making. Justification for the duration of each
phase will address the on-site availability of equipment, the resources necessary
to deploy the equipment consistent with the required timeline, anticipated site
conditions following the beyond-design-basis external event, and the ability of the
local infrastructure to enable delivery of equipment and resources from offsite.
During an ELAP, cooling to the RCP seal packages will be lost and water at high temperatures
may degrade seal materials leading to excess seal leakage from the RCS. Without ac power
available to the emergency core cooling system, inadequate core cooling may eventually result
from the leakage out of the seals. The ELAP analysis credits operator actions to align highpressure RCS makeup sources and replenish the RCS inventory in order to ensure the core is
covered with water, thus precluding inadequate core cooling. The amount of high pressure
RCS makeup needed is mainly determined by the seal leakage rate. Therefore, the seal
leakage rate is of primary importance in an ELAP analysis as greater values of the leakage
rates will result in a shorter time period for the operator action to align the high pressure RCS
makeup water sources.
The licensee provided an SOE in its Integrated Plan, which included the time constraints and
the technical basis for its site. The SOE is based on an analysis in Section 5.2.1 of WCAP17601-P that assumes a RCP seal leakage rate of 21 gpm per pump. WCAP-17601-P
considers this seal leakage rate applicable to Westinghouse plants with a standard
Westinghouse RCP seal design. However, as noted above, the licensee indicated that all seals
on the Westinghouse Model 93A RCPs at North Anna will eventually be modified to use
Flowserve N-9000 seals with the Abeyance feature. The modified seal design is expected to
result in significantly reduced leakage relative to the standard seal design for events involving
an extended loss of seal cooling. However, adequate justification has not yet been presented to
the NRC staff to justify the low-leakage performance of the Flowserve N-9000 seals with the
Abeyance feature.
Providing adequate justification for the assumed RCP seal leakage rates during an ELAP event
was identified as a generic concern by the NRC staff. This concern was addressed by the
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industry in the following submittals:
•
WCAP-17601-P, Revision 1, “Reactor Coolant System Response to the
Extended Loss of AC Power Event for Westinghouse, Combustion
Engineering and Babcock & Wilcox NSSS Designs” dated January 2013
(ADAMS Accession No. ML13042A011 and ML13042A013 (Non-Publically
Available)).
A position paper dated August 16, 2013, entitled “Westinghouse Response to
NRC Generic Request for Additional Information (RAI) on Reactor coolant
(RCP) Seal Leakage in Support of the Pressurized Water Reactor Owners
Group (PWROG)” (ADAMS Accession No. ML13190A201 (Non-Publically
Available)).
After reviewing these submittals, the NRC staff placed certain limitations on Westinghouse
designed plants. Those limitations and their applicability are discussed below in light of designspecific information pertaining to the reactors at North Anna:
1.
For the plants using Westinghouse RCPs and seals that are not the SHIELD shutdown
seals, the RCP seal initial maximum leakage rate should be greater than or equal to the
upper bound expectation for the seal leakage rate for the ELAP event (21 gpm/seal)
discussed in the PWROG white paper addressing the RCP seal leakage for
Westinghouse plants. If the RCP seal leakage rates used in the plant-specific ELAP
analyses are less than the upper bound expectation for the seal leakage rate discussed
in the whitepaper, justification should be provided. If the seals are changed to nonWestinghouse seals, the acceptability of the use of non-Westinghouse seals should be
addressed, and the RCP seal leakage rates for use in the ELAP analysis should be
provided with acceptable justification. The licensee has assumed a seal leakage rate of
21 gpm per reactor coolant pump seal for North Anna. Furthermore, an open item is
identified below relative to the need to provide a basis for the leakage rate associated
with the Flowserve N-9000 seals with the Abeyance feature. Therefore, the staff
considers this item associated with leakage rates less than 21 gpm to be addressed for
North Anna.
2.
In some plant designs, such as those with 1200 to 1300 psia SG design pressures and
no accumulator backing of the main steam system power-operated relief valve (PORV)
actuators, the cold legs could experience temperatures as high as 580 0F before
cooldown commences. This is beyond the qualification temperature (550 0F) of the Orings used in the RCP seals. For those Westinghouse designs, a discussion of the
information (including the applicable analysis and relevant seal leakage testing data)
should be provided to justify that (1) the integrity of the associated O-rings will be
maintained at the temperature conditions experienced during the ELAP event, and (2)
the seal leakage rate of 21 gpm/seal used in the ELAP is adequate and acceptable.
Based upon information provided by the licensee during the audit, the SG poweroperated relief valves’ nominal opening setpoint is 1035 psig. This implies a steam
generator temperature of approximately 550 °F, and hence a slightly higher cold leg
temperature during single-phase natural circulation, but one which is also roughly 550
°F. Furthermore, as addressed via an open item below, specific qualification testing for
the Flowserve N-9000 seals with the Abeyance feature will be reviewed by the staff to
ensure that the performance of these seals has been qualified for the conditions
applicable to North Anna. As such, the staff considers this item associated with O-ring
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qualification for plants with elevated SG design pressures to be addressed for North
Anna.
3.
Some Westinghouse plants have installed or will install the SHIELD shutdown seals, or
other types of low leakage seals, and have credited or will credit a low seal leakage rate
(e.g., 1 gpm/seal) in the ELAP analyses for the RCS response. For those plants,
information should be provided to address the impacts of the Westinghouse 10 CFR Part
21 report, “Notification of the Potential Existence of Defects Pursuant to 10 CFR Part
21,” dated July 26, 2013 (ADAMS No. ML13211A168) on the use of the low seal leakage
rate in the ELAP analysis. The licensee’s Integrated Plan does not currently credit low
leakage seals in the ELAP analyses. Therefore this item is currently not applicable for
North Anna.
4.
If the seals are changed to the newly designed Generation 3 SHIELD seals, or nonWestinghouse seals, the acceptability of the use of the newly designed Generation 3
SHIELD seals, or non-Westinghouse seals should be addressed, and the RCP seal
leakages rates for use in the ELAP analysis should be provided with acceptable
justification. The PWROG is working on these issues and will submit to the NRC
position papers that will contain test data regarding the maximum seal leakage rates of
Generation 3 SHIELD seals and Flowserve N-9000 seals. The NRC staff will review
these position papers upon their receipt. Resolution of the generic concern associated
with the acceptability of the Flowserve N-9000 seals with the Abeyance feature and the
determination of an appropriate leak rate is identified as Open Item 3.2.1.2.B for North
Anna in Section 4.2 below.
The NRC staff also requested during the audit that the licensee address issues concerning the
response of the pump seal to a restoration of seal cooling and the potential for increased stress
and degradation of the seal during a cooldown of the reactor coolant system. The licensee
stated that event response procedures for an ELAP will be the same as currently used for the
station blackout event; however, the staff’s review identified that this response lacked the
following information: (1) the basis for concluding that the station blackout analysis had
acceptably addressed the issues of concern to the staff, (2) the significant difference in time
duration between the station blackout and ELAP events, and (3) the proposed reactor coolant
pump seal design modification. Therefore, the staff designated Confirmatory Item 3.2.1.2.C in
Section 4.2, below, for the licensee to:
(1) Confirm that stresses resulting from a cooldown of the RCS will not result in the failure of
seal materials.
(2) As applicable, confirm that reestablishing cooling to the seals will not result in increased
leakage due to thermal shock.
The staff further noted that the licensee’s depressurization terminus for North Anna is 290 psig
in the steam generators, which is slightly in excess of the 300 psia value that was assumed in
the analysis in Section 5.2.1 of WCAP-17601-P. The staff considered the effect of this slight
pressure difference on the seal leakage rate to be insignificant relative to the expected
conservatism of assuming a 21-gpm seal leakage rate in light of the planned installation of lowleakage seals.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01 and subject to the successful
closure of issues related to the Confirmatory and Open Items, provides reasonable assurance
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that the requirements of Order EA-12-049 will be met with respect to RCP seal leakage rates, if
these requirements are implemented as described.
3.2.1.3 Decay Heat
NEI Section 3.2.1.2 states in part:
The initial plant conditions are assumed to be the following:
(1) Prior to the event the reactor has been operating at 100 percent rated thermal
power for at least 100 days or has just been shut down from such a power
history as required by plant procedures in advance of the impending event.
Engineering Technical Evaluation, ETE-NAF-2012- 0150, Revision 0, “Evaluation of Core
Cooling Coping for Extended Loss of AC Power (ELAP) and Proposed Input for Dominion’s
Response to NRC Order EA-12-049 for Dominion Fleet,” documents the technical basis for the
core cooling coping time for North Anna. The design inputs and assumptions for this document
include the initial plant condition that the reactor has been operating at 100 percent rated
thermal power for at least 100 days prior to the event or has just been shut down from such a
power history as required by plant procedures in advance of the impending event.
The NRC staff further understands that the generic analysis in Section 5.2.1 of WCAP-17601-P
that is being referenced by the licensee for North Anna computed decay heat based on the ANS
5.1-1979 decay heat model with a two-sigma adder. This model includes fission product decay
heat resulting from the fission of U-235, U-238, and Pu-239, as well as actinide decay heat from
U-239 and Np-239.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to decay heat, if
these requirements are implemented as described.
3.2.1.4
Initial Values for Key Plant Parameters and Assumptions
NEI 12-06, Section 3.2 provides a series of assumptions to which initial key plant parameters
(core power, RCS temperature and pressure, etc.) should conform. When considering the code
used by the licensee and its use in supporting the required event times for the SOE, it is
important to ensure that the initial key plant parameters not only conform to the assumptions
provided in NEI 12-06, Section 3.2, but that they also represent the starting conditions of the
code used in the analyses and that they are included within the code’s range of applicability.
On pages 6 and 7 of the Integrated Plan, in regards to the boundary conditions and initial plant
conditions and assumptions established to support development of FLEX strategies, the
licensee included all of the relevant baseline assumptions contained in NEI 12-06.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to initial values for
key plant parameters and assumptions, if these requirements are implemented as described.
3.2.1.5
Monitoring Instrumentation and Controls
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NEI 12-06, Section 3.2.1.10 states in part:
The parameters selected must be able to demonstrate the success of the
strategies at maintaining the key safety functions as well as indicate imminent or
actual core damage to facilitate a decision to manage the response to the event
within the Emergency Operating Procedures and FLEX Support Guidelines or
within the SAMGs. Typically, these parameters would include the following:
•
•
•
•
•
•
SG Level
SG Pressure
RCS Pressure
RCS Temperature
Containment Pressure
SFP Level
The plant-specific evaluation may identify additional parameters that are needed
in order to support key actions identified in the plant procedures/guidance or to
indicate imminent or actual core damage.
On pages 24 and 25 of the Integrated Plan, the licensee listed the installed instrumentation
credited for maintaining core cooling and heat removal during Phase 1 of an ELAP. Phase 2
and 3 strategies rely on the same key instrumentation. Available measured parameters include
AFW flowrate, SG level, SG pressure, RCS hot and cold leg temperatures, core exit
thermocouple temperature, and ECST level.
On pages 37 and 38 of the Integrated Plan, the licensee listed the installed instrumentation
credited to maintain RCS inventory control during Phase 1 of an ELAP. Phase 2 and 3
strategies rely on the same key instrumentation. Available measured parameters and
instruments include SG pressure, RCS hot leg and cold leg temperatures, pressurizer level,
reactor vessel level indication, and excore nuclear instruments.
On pages 47 and 48 of the Integrated Plan, the licensee listed the containment pressure and
containment wide range temperature as measured parameters that would be available through
all phases of the ELAP.
On page 53 of the Integrated Plan, the licensee listed SFP level as a measured parameter that
would be available through all phases of the ELAP event.
On page 61 of the Integrated Plan, the licensee stated that the Phase 1 strategy involves
extending the available electrical power from the installed Class 1E 125 VDC batteries through
reduction of DC bus loading soon after the occurrence of an ELAP/LUHS by stripping nonessential loads from the 125 VDC and the battery-backed 120 VAC vital buses. Essential
instrumentation necessary for key parameter monitoring is powered by the 120 VAC vital bus
circuits, which will be maintained energized by 125 VDC battery bus through the Class 1E
inverters following an ELAP.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01 and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to monitoring
instrumentation and controls, if these requirements are implemented as described.
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3.2.1.6
Sequence of Events
NEI 12-06, Section 3.2.1.7, Item 6 states:
Strategies that have a time constraint to be successful should be identified and a
basis provided that the time can reasonably be met.
The SOE is discussed in the integrated plan on pages 8 through 13 and in Attachment 1A on
pages 110 and 111.
On page 8 of the Integrated Plan, the licensee stated that the sequence of events timeline is
provided in Attachment 1A and provided the following explanation:
Preliminary estimates of response times have been developed based on plant
simulator runs and table-top walkthroughs of planned actions. A 2-hour duration
is assumed for deployment of equipment from the BDB Storage Building(s)
based on a "sunny day" validation for implementation of CFR 50.54(hh)(2) time
sensitive actions. The validation included deploying a portable high capacity
pump from its storage location to a location near the Service Water Reservoir
(staging location) and routing hoses to provide flow to the spent fuel pool. Time
to clear debris to allow equipment deployment is assumed to be 2 hours, and will
depend on the location of the BDB Storage Building(s). This time is considered
to be reasonable based on site reviews and proposed locations of the BDB
Storage Building(s). Debris removal equipment will be stored in the BDB Storage
Building(s). Validation of assumed response times included in Attachment 1A
will be completed once FSGs have been developed and will include a staffing
analysis.
Validation of the response times is identified as Confirmatory Item 3.2.1.6.A in Section
4.2 below.
On pages 9 through 13 of the Integrated Plan, as modified by the six-month update dated
August 23, 2013, and the supplement to the OIP dated April 30, 2013, the licensee detailed
strategies that had a time constraint and provided the basis that the strategies could reasonably
be met.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01 and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to the sequence of events, if these
requirements are implemented as described.
3.2.1.7
Cold Shutdown and Refueling
NEI 12-06, Table 1-1, lists the coping strategy requirements as presented in Order EA-12049. Item (4) of that list states:
Licensee or CP holders must be capable of implementing the strategies in all
modes
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The generic concern related to shutdown and refueling requirements is applicable to North
Anna. This generic concern has been resolved through the NRC endorsement of NEI position
paper entitled “Shutdown/Refueling Modes” (ADAMS Accession No. ML13273A514); and has
been endorsed by the NRC in a letter dated September 30, 2013 (ADAMS Accession No.
ML13267A382).
The position paper describes how licensees will, by procedure, maintain equipment available for
deployment in shutdown and refueling modes. The NRC staff concluded that the position paper
provides an acceptable approach for demonstrating that licensees are capable of implementing
mitigating strategies in all modes of operation.
The licensee informed the NRC staff of its intent to abide by the generic resolution.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to cold shutdown and refueling, if
these requirements are implemented as described.
3.2.1.8
Core Sub-Criticality
NEI 12-06 Table 3-2 states in part:
All plants provide means to provide borated RCS makeup.
On page 36 of the Integrated Plan, the licensee stated
In general, the FLEX strategy for RCS inventory control / reactivity management
relies on RCP seal leakage being sufficiently low for initial control of RCS
inventory, isolation of the RCS as directed by the emergency procedure, and
cooldown limitations to limit reactivity addition. With these controls in place, no
RCS makeup or boration is required for the first 33 hours of an ELAP / LUHS
event. …
Reactivity:
The emergency procedure for the loss of all AC power, ECA-0.0, provides
direction for the Operator to initiate an RCS cooldown using the SG PORVs to a
steam generator pressure of approximately 290 psig which equates to an RCS
core inlet temperature of approximately 419 degrees F. At this RCS temperature,
analysis indicates that at the most limiting core condition, additional RCS
boration is not needed to ensure adequate Shutdown Margin (SDM), e.g.,
reactivity <0.99, is maintained for the first 37 hours without boration. The most
limiting core condition is the highest core burnup, which occurs at end of EOC.
In the 6-month update to the Integrated Plan, the licensee stated:
Changes to the timing of the RCS injection strategy have been made. The
strategy for RCS injection for inventory and reactivity control has been moved
from a Phase 3 activity to a Phase 2 activity. The details and descriptions
provided in Section C.3 of the Integrated Plan for RCS injection for the Phase 3
activity continue to be the same for the Phase 2 strategy for RCS injection,
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including the time at which natural circulation capability is lost, i.e., approximately
33 hours based on WCAP-17601 and ETE-NAF-2012-0150. For conservatism
and margin to account for uncertainty within the calculations and unanticipated
deployment issues, a time of 16 hours has been chosen, which provides
significant margin (by a factor of 2) prior to loss of natural circulation and the start
of reflux boiling.
As noted previously, the time constraint of 33 hours for providing makeup to the reactor coolant
system was an industry-determined value from analysis performed in WCAP-17601-P. The
definitions and rationale underlying the selection of 33 hours as the time of entry into the reflux
condensation cooling mode, which is regarded as the triggering point for providing makeup to
the reactor coolant system, have not been adequately justified to the staff. Likewise, as
reflected above in Confirmatory Item 3.2.1.1.A, at the present time, the provision of makeup at
16 hours has not been demonstrated to be sufficient to avoid entry into the reflux condensation
cooling mode. Furthermore, based upon the licensee’s planned installation of low-leakage
seals, the planned timing of makeup appears reasonable; however, the performance of the N9000 seals with the Abeyance feature is currently Open Item 3.2.1.2.B.
Review of the Integrated Plan revealed that a generic concern associated with the modeling of
the timing and uniformity of the mixing of a liquid boric acid solution injected into the RCS under
natural circulation conditions potentially involving two-phase flow was applicable to the licensee.
The PWROG submitted to the NRC a position paper, dated August 15, 2013 (withheld from
public disclosure for proprietary reasons), which provides test data regarding boric acid mixing
under single-phase natural circulation conditions and outlines applicability conditions intended to
ensure that boric acid addition and mixing would occur under conditions similar to those for
which boric acid mixing data is available. However at the time of the licensee’s audit responses
to support this review, the NRC staff had not endorsed the August 15, 2013 PWROG position
paper.
In response to a question concerning the boric acid mixing model raised by the NRC staff during
the audit, the licensee stated that:
The uniform mixing model is used for the North Anna ELAP analysis. This
analysis is consistent with the method in the PWROG white paper related to the
boron mixing model. The North Anna analysis shows that no boron addition is
required to offset the cooldown of the core to the inlet temperature corresponding
to a secondary pressure of 290 psig. Boration is not required until approximately
37 hours into the transient to account for Xenon decay. The inventory control
strategy will deploy the BDB RCS Injection pump for RCS make-up with borated
water approximately 16 hours into the event. Mass addition via the BDB RCS
Injection pump will forestall natural circulation flow breakdown and the transition
to reflux cooling and restore levels into the pressurizer. Therefore, boron injected
into the RCS will mix via turbulent natural circulation flow and would be expected
to provide an essentially uniform boron concentration in the reactor coolant
system well before any boron concentration increase is needed for reactivity
control. Per Calculation CAL-MISC-11788, the total amount of RWST water that
is required to offset the complete decay of Xenon (which occurs at a time greater
than 100 hours) is 5,200 gallons. At 40 gpm, the time necessary to inject this
amount of borated water (at the RWST concentration or 2600 ppm) is less than
2.25 hours.
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The licensee’s approach for modeling boric acid mixing, as described above, is based upon a
method described in the PWROG position paper that the NRC staff had not yet endorsed at the
time of the audit discussions with the licensee. Since this time, the NRC endorsed the PWROG
position paper but with several clarifications (ADAMS Accession No. ML13276A183).
Therefore, the staff considers the modeling of boric acid mixing to be Open Item 3.2.1.8.A for
North Anna for the licensee to address the clarifications and alignment with the NRC
endorsement letter dated January 8, 2014.
In response to a question concerning the reactivity analysis for North Anna that was raised by
the NRC staff during the audit, the licensee stated that
CAL-MISC-11788 is the North Anna reactivity analysis which verified the reactor
remains sub-critical for the limiting conditions of the ELAP. As noted in the
assumptions of the calculation, no accumulator injection was credited which
represents the no leakage case. The information in this response will be
provided in the February 2014 Six-Month Status Update.
As described above, the licensee has not completed reactivity calculations for North Anna for a
case with no reactor coolant system leakage. Furthermore, as reflected by the fact that the staff
did not endorse the PWROG position paper on boron mixing, the staff has not concluded that
the no-leakage case is limiting with respect to ensuring adequate shutdown margin. Therefore,
completion of calculations demonstrating adequate shutdown margin for North Anna in ELAP
scenarios with and without seal leakage is identified as Confirmatory Item 3.2.1.8.B in Section
4.2.
Shutdown margin calculations typically rely on boration curves that are cycle specific. In such
cases, cycle-specific verification of shutdown margin calculations is necessary because the
negative reactivity insertion requirements are a function of the core design, which generally
varies from operating cycle to operating cycle. Based upon a review of the licensee’s relevant
calculations, it appears that the shutdown margin calculations for North Anna are based on a
specific core design, and that the licensee has recognized the need to validate whether
adjustments are required for future cores. However, it is not clear that an adequate method of
verification has been developed and whether, in fact, the licensee will confirm that shutdown
margin calculations remain bounding for each future operating cycle. This is identified as
Confirmatory Item 3.2.1.8.C in Section 4.2.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01 and, subject to the successful
closure of issues related to the Open and Confirmatory Items, provides reasonable assurance
that the requirements of Order EA-12-049 will be met with respect to core sub-criticality, if these
requirements are implemented as described.
3.2.1.9 Use of Portable Pumps
NEI 12-06, Section 3.2.2, Guideline (13), states in part:
Regardless of installed coping capability, all plants will include the ability to use
portable pumps to provide RPV/RCS/SG makeup as a means to provide diverse
capability beyond installed equipment. The use of portable pumps to provide
RPV/RCS/SG makeup requires a transition and interaction with installed
systems. For example, transitioning … to a portable pump for SG makeup may
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require cooldown and depressurization of the SGs in advance of using the
portable pump connections. Guidance should address both the proactive
transition from installed equipment to portable and reactive transitions in the
event installed equipment degrades or fails. Preparations for reactive use of
portable equipment should not distract site resources from establishing the
primary coping strategy. In some cases, in order to meet the time-sensitive
required actions of the site-specific strategies, the FLEX equipment may need to
be stored in its deployed position.
The fuel necessary to operate the FLEX equipment needs to be assessed in the
plant specific analysis to ensure sufficient quantities are available as well as to
address delivery capabilities.
NEI 12-06 Section 11.2 states in part:
Design requirements and supporting analysis should be developed for portable
equipment that directly performs a FLEX mitigation strategy for core,
containment, and SFP that provides the inputs, assumptions, and documented
analysis that the mitigation strategy and support equipment will perform as
intended.
On page 26 of the Integrated Plan, the licensee stated that the Phase 2 strategy for reactor core
cooling and heat removal provides an indefinite supply of water for feeding SGs and a portable,
diesel-driven backup AFW pump for use in the event that the fire protection system water makeup source and/or the TDAFW pump becomes unavailable.
In the six-month update to the Integrated Plan, the licensee stated that changes to the timing of
the RCS injection strategy have been made. The strategy for RCS injection for inventory and
reactivity control has been moved from a Phase 3 activity to a Phase 2 activity. North Anna will
purchase and store two BDB RCS Injection Pumps for use in the Phase 2 RCS Inventory
strategy. However, the licensee did not clarify how the two BDB RCS injection pumps conform
to NEI 12-06, paragraph following Section 3.2.2, Guideline 15 which states in part: “In order to
ensure reliability and availability of the FLEX equipment required to meet these capabilities, the
site should have sufficient equipment to address all functions at all units on-site, plus one
additional spare, i.e., N+1 capability, where N is the number of units on-site.” This is identified
as Confirmatory Item 3.2.1.9.A in Section 4.1 below.
During the audit, the licensee was requested to clarify whether a single FLEX pump will be used
to provide cooling flow to multiple destinations (e.g., the reactor core, SGs, and the SFP). If so,
the licensee was requested to confirm that the FLEX pump can supply adequate flow and clarify
whether the pumped flow will be split and simultaneously supplied to all destinations or whether
the flow will be alternated between them. If simultaneous flow will be used, the licensee was
requested to clarify how the flow splits will be measured and controlled (i.e., whether control
exists for the total flow on a common line or on lines to individual destinations) to ensure that
adequate flow (i.e., sufficient but not excessive) reaches each destination.
In response, the licensee stated that:
The BDB high capacity pump is capable of providing makeup to both the Unit 1
and Unit 2 AFW systems for SG injection, as well as makeup water to the dual
unit SFP, to accomplish the associated FLEX strategies. The BDB high capacity
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pump has the ability to draw water from the circulating water discharge canal,
Lake Anna, or the Service Water reservoir. A single BDB high capacity makeup
pump has a minimum capacity of 1200 gpm at 100 psi. Preliminary hydraulic
analysis of the BDB high capacity pump and the associated hoses and installed
piping systems confirm that the BDB high capacity pump capabilities exceed the
FLEX strategy requirements for AFW supply and SPF makeup given below:
Unit 1 BDB AFW Requirement--------------300 gpm
Unit 2 BDB AFW Requirement--------------300 gpm
Spent Fuel Pool Makeup Requirement----500 gpm
The BDB high capacity pump discharge hydraulic hose network designed for
splitting the flow to the three loads listed above is shown in Figure 2 of ETECPR-2012-0012, Appendix B. Flow may be controlled in both the common
supply hose, i.e., the discharge hose from the BDB high capacity pump, and in
each individual branch line into which the flow splits off. Flow is controlled in the
pump discharge hose by controlling the speed of the BDB high capacity pump
and/or opening the discharge recirculation line to send a portion of the discharge
overboard. Flow splits in the branches are controlled and monitored by various
means as follows:
Flow is controlled in the branch line to the SFP by throttling the branch line gated
wye discharge valve and/or in-line shutoff valve. Flow to the SPF is monitored by
observing SPF level and throttling the branch line flow to reach equilibrium with
the SFP boiloff after returning the SFP level to normal level. Alternately, flow to
the SFP may be periodically batched to maintain SFP in an acceptable level
range, as the limiting SFP boil off rate is calculated to be only 101 gpm
(Calculation MISC-11792).
Flow is controlled in the branch line to fill each unit’s ECST by throttling the
branch line gated wye discharge valve, and/or the AFW distribution manifold
discharge valve, and/or the two isolation (ball) valves in the mechanical
connection to the ESCT. Flow to the ECST is monitored by observing ECST
level indication and throttling the branch line flow to reach equilibrium with the
flow demand of the TD AFW pump that is taking suction from the ECST and
delivering AFW to the steam generators for core cooling and decay heat removal.
Alternately, flow to the ECST may be periodically batched to maintain ECST level
in a desired range, especially when the TD AFW pump flow demands are low
due to decreasing decay heat removal requirements. TD AFW pump flow
demand is monitored directly by AFW flow indication in the MCR and indirectly by
steam generator level indication in the MCR.
Flow is controlled in the branch line to supply each unit’s BDB AFW pump by
throttling the branch supply line gated wye discharge valve, and/or the branch
supply line AFW distribution manifold discharge valve, and/or the AFW system
boundary isolation (globe) valve in the mechanical connection to the AFW pump
discharge header. BDB AFW pump flow is monitored directly by flow indication
in the discharge header of the BDB AFW pump on the pump trailer, directly by
AFW flow indication in the MCR, and indirectly by steam generator level
indication in the MCR.
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Phase 2 and Phase 3 FLEX strategy for RCS inventory and core reactivity
control is that the borated water from the RWST is injected into the RCS from the
BDB RCS Injection pump. The BDB RCS injection pump is a positive
displacement pump with a nominal capacity of 45 gpm. RCS injection flow is
monitored by pump flow indication on the BDB RCS Injection pump trailer and
controlled by varying the speed diesel engine/pump and/or recirculating a portion
of the pump flow back to the suction via the recirculation line.
The BDB RCS Injection pump hose network (see Figure 2 of ETE-CPR-20120012, Appendix B) is a different hose network than that for providing for SFP
makeup and AFW supply described above. If the RWST is depleted or
unavailable, the BDB RCS Injection pump may be supplied by an alternate
borated water source or take suction from the portable boron mixing tank. The
portable boron mixing tank is filled by a clean water source, or from the discharge
of the BDB High Capacity pump, and bags of boric acid are manually added to
and mixed in the tank. Filling the portable boron mixing tank is a manual
batching operation that requires no flow indication. If the BDB High Capacity
pump is used to fill the portable boron mixing tank, it has sufficient excess
capacity from the margin above its SFP makeup and AFW supply requirements
to supply water to the portable boron mixing tank for one or both units.
Calculations documenting the AFW supply, SFP makeup, and RCS inventory
hydraulic analysis, originally scheduled to be completed by September 2013 (OIP
OI # 5), will be completed later this year and available on the Dominion ePortal at
that time. The change in the calculation completion date does not impact the
Order implementation date.
The licensee’s response regarding flow splitting appears to be a reasonable plan; however, the
staff noted that completion of the hydraulic analysis is outstanding. Completion of the hydraulic
analysis is designated as Confirmatory Item 3.2.1.9.B in Section 4.2 below.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory and Open Items, provides reasonable assurance
that the requirements of Order EA-12-049 will be met with respect to use of portable pumps, if
these requirements are implemented as described.
3.2.2
Spent Fuel Pool Cooling Strategies
NEI 12-06, Table 3-2 and Appendix D summarize one acceptable approach for the SFP cooling
strategies. This approach uses a portable injection source to provide 1) makeup via hoses on
the refuel deck/floor capable of exceeding the boil-off rate for the design basis heat load; 2)
makeup via connection to spent fuel pool cooling piping or other alternate location capable of
exceeding the boil-off rate for the design basis heat load; and alternatively 3) spray via portable
monitor nozzles from the refueling deck/floor capable of providing a minimum of 200 gallons per
minute (gpm) per unit (250 gpm to account for overspray). This approach will also provide a
vent pathway for steam and condensate from the SFP.
As described in NEI 12-06, Section 3.2.1.7 and JLD-ISG-2012-01, Section 2.1, strategies that
have a time constraint to be successful should be identified and a basis provided that the time
can be reasonably met. NEI 12-06, Section 3 provides the performance attributes, general
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criteria, and baseline assumptions to be used in developing the technical basis for the time
constraints. Since the event is a beyond-design-basis event, the analysis used to provide the
technical basis for time constraints for the mitigation strategies may use nominal initial values
(without uncertainties) for plant parameters, and best-estimate physics data. All equipment
used for consequence mitigation may assume to operate at nominal setpoints and capacities.
NEI 12-06, Section 3.2.1.2 describes the initial plant conditions for the at-power mode of
operation; Section 3.2.1.3 describes the initial conditions; and Section 3.2.1.6 describes SFP
initial conditions.
NEI 12-06, Section 3.2.1.1 provides the acceptance criterion for the analyses serving as the
technical basis for establishing the time constraints for the baseline coping capabilities
described in NEI 12-06, which provide an acceptable approach to meeting the requirements of
EA-12-049 for maintaining SFP cooling. This criterion is keeping the fuel in the SFP covered.
On page 53 of the Integrated Plan, the licensee stated that evaluations estimate that with no
operator action following a loss of SFP cooling at the maximum design heat load, the SFP will
reach 212 degrees F in approximately 9 hours and boil off to a level 10 feet above the top of fuel
in 43 hours from initiation of the event. Therefore, the Phase 1 coping strategy for spent fuel
pool cooling is to monitor spent fuel pool level using instrumentation to be installed as required
by NRC Order EA-12-051. No additional modifications are required other than installation of the
BDB Spent Fuel Pool level monitoring instruments as required by NRC Order EA-12-051.
On page 55 of the Integrated Plan, the licensee stated that the primary FLEX strategy for SFP
cooling is to continuously monitor SFP level. Within the first 24 hours of the BDB event, the
BDB high capacity pump will be staged and connected to the external SFP makeup connection
installed outside the Fuel Building to provide SFP makeup capabilities up to 500 gpm, which
exceeds the boil-off rate of 101 gpm. The alternate FLEX strategy utilizes the diesel driven fire
pump to pressurize the fire main, which provides makeup to the SFP via the 6" emergency
makeup line. This makeup strategy does not require entry into the Fuel Building. An existing
spray strategy provides a means to spray water to the SFP at a rate of 500 gpm. The strategy
provides makeup flow through either fire hose run over the side of the SFP or spray monitors
set up on the SFP deck fed by the fire main or the BDB High Capacity pump. When deployed,
two spray monitors are connected via a wye that splits the pump supply into two (2) 3-inch
hoses. The two 3-inch spray monitor hoses will be routed from the New Fuel storage area to
the SFP. The two oscillating spray monitors will be set up 30 feet apart and 16 feet back from
the SFP to spray water into the SFP to maintain water level. The suction sources for the BDB
High Capacity pump are the SW Reservoir or Lake Anna.
On page 55 of the Integrated Plan, the licensee stated that following a BDB event, a vent
pathway would be required in the event of SFP bulk boiling and can be established by opening
the Fuel Building roll-up doors for inlet and outlet air flow. However the licensee does not
provide a technical justification that confirms opening of the roll-up doors would provide an
adequate ventilation path for the SFP area. This is identified as Confirmatory Item 3.2.2.A in
Section 4.2 below.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and, subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to SFP cooling strategies, if these
requirements are implemented as described.
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3.2.3
Containment Functions Strategies
NEI 12-06, Table 3-2 and Appendix D provide some examples of acceptable approaches for
demonstrating the baseline capability of the containment strategies to effectively maintain
containment functions during all phases of an ELAP. One of these acceptable approaches is by
analysis.
The North Anna units are both dry, sub-atmospheric-type containments, and the licensee
performed calculations to demonstrate that no actions would be required to remove heat and
protect the containment functions in the first seven days following an ELAP event.
On page 47 of the Integrated Plan, the licensee stated that the Phase 1 coping strategy for
containment involves verifying containment isolation per ECA-0.0, Loss of All AC Power, and
continuing to monitoring containment pressure using installed instrumentation. Evaluations
have concluded that containment temperature and pressure will remain below design limits and
key parameter instruments subject to the containment environment will remain functional for at
least 7 days. Calculation MISC-11793, "Evaluation of Long Term Containment Pressure and
Temperature Profiles Following Loss of Extended AC Power (ELAP)" was referenced in the
Integrated Plan to support the above conclusion. This calculation utilized Gothic version 7.2a to
perform the calculation. Assumptions included in the calculation were standard Westinghouse
RCP seal leakage of 21 gpm per pump, plus 1 gpm unidentified leakage, for a total leakage of
64 gpm.
On page 50 of the Integrated Plan, the licensee stated that further analysis is required to
determine the strategy and time requirements, if any, for actions to reduce containment
pressure and temperature beyond seven days. As such, the Phase 3 coping strategy to
maintain containment integrity is under development. Methods to monitor and evaluate
containment conditions and depressurize/cool containment, if necessary, will be provided in a
future update. This is identified as Confirmatory Item 3.2.3.A in Section 4.2 below.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01 and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to containment function strategies, if
these requirements are implemented as described.
3.2.4
Support Functions
3.2.4.1 Equipment Cooling – Cooling Water
NEI 12-06, Section 3.2.2, Guideline (3) states:
Plant procedures/guidance should specify actions necessary to assure that
equipment functionality can be maintained (including support systems or
alternate method) in an ELAP/LUHS or can perform without ac power or normal
access to the UHS.
Cooling functions provided by such systems as auxiliary building cooling water,
service water, or component cooling water may normally be used in order for
equipment to perform their function. It may be necessary to provide an alternate
means for support systems that require ac power or normal access to the UHS,
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or provide a technical justification for continued functionality without the support
system.
In the Integrated Plan, the licensee did not discuss the need for additional strategies to provide
cooling functions for equipment to assure that coping strategy functionality could be maintained.
During the audit process, the licensee stated that permanently installed plant equipment to
support FLEX strategies do not require cooling support systems to perform their required
functions.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01 and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to equipment cooling, if these
requirements are implemented as described.
3.2.4.2 Ventilation – Equipment Cooling
NEI 12-06, Section 3.2.2, Guideline (10) states in part:
Plant procedures/guidance should consider loss of ventilation effects on specific
energized equipment necessary for shutdown (e.g., those containing internal
electrical power supplies or other local heat sources that may be energized or
present in an ELAP.
ELAP procedures/guidance should identify specific actions to be taken to ensure
that equipment failure does not occur as a result of a loss of forced
ventilation/cooling. Actions should be tied to either the ELAP/LUHS or upon
reaching certain temperatures in the plant. Plant areas requiring additional air
flow are likely to be locations containing shutdown instrumentation and power
supplies, turbine-driven decay heat removal equipment, and in the vicinity of the
inverters. These areas include: steam driven AFW pump room, … the control
room, and logic cabinets. Air flow may be accomplished by opening doors to
rooms and electronic and relay cabinets, and/or providing supplemental air flow.
Air temperatures may be monitored during an ELAP/LUHS event through
operator observation, portable instrumentation, or the use of locally mounted
thermometers inside cabinets and in plant areas where cooling may be needed.
Alternatively, procedures/guidance may direct the operator to take action to
provide for alternate air flow in the event normal cooling is lost. Upon loss of
these systems, or indication of temperatures outside the maximum normal range
of values, the procedures/guidance should direct supplemental air flow be
provided to the affected cabinet or area, and/or designate alternate means for
monitoring system functions.
For the limited cooling requirements of a cabinet containing power supplies for
instrumentation, simply opening the back doors is effective. For larger cooling
loads, such as … AFW pump rooms, portable engine-driven blowers may be
considered during the transient to augment the natural circulation provided by
opening doors. The necessary rate of air supply to these rooms may be
estimated on the basis of rapidly turning over the room’s air volume.
Actuation setpoints for fire protection systems are typically at 165-180°F. It is
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expected that temperature rises due to loss of ventilation/cooling during an
ELAP/LUHS will not be sufficiently high to initiate actuation of fire protection
systems. If lower fire protection system setpoints are used or temperatures are
expected to exceed these temperatures during an ELAP/LUHS,
procedures/guidance should identify actions to avoid such inadvertent actuations
or the plant should ensure that actuation does not impact long term operation of
the equipment.
On page 92 of the Integrated Plan, the licensee stated that the FLEX strategies for maintenance
and/or support of safety functions involve several elements. One element is to ensure that
ventilation, heating, and cooling is adequate to maintain acceptable environmental conditions for
equipment operation and personnel habitability. In the six-month update (Item #13) and during
the audit process, the licensee stated that the finalized details of the ventilation strategy are still
under development and will conform to the guidance given in NEI 12-06. The details of this
strategy will be provided at a later date. This is identified as Confirmatory Item 3.2.4.2.A in
Section 4.2 below.
During the audit, the licensee was requested to provide information on the adequacy of
the ventilation provided in the battery room to protect the batteries from the effects of
extreme high and low temperatures.
In response, the licensee stated:
In the case of an ELAP event, the Class 1E battery buses will be load stripped
within 1.5 hours after initiation of the event in order to provide for an extended
Phase 1 battery life of 8 hours. During battery discharge in Phase 1 of the ELAP
scenario, heat addition internal to the battery rooms is negligible. The four
battery rooms (per unit) are rooms with concrete walls partitioned out of the
Control Room (CR) envelope. Two battery rooms are in the Emergency
Switchgear Room (ESGR) and two are in the Cable Spreading Room above the
CR. The ventilation for the battery rooms in the ESGR flows from the ESGR into
the room, and then outside through the normal exhaust fan. For the Battery
rooms above the CR, air is drawn from the CR and exhausted back to the CR.
While the battery rooms are not modeled in the loss of ventilation transient
analysis model, Calculation ME-0972, Rev. 0 shows that the expected loss of
ventilation transient temperatures in the ESGR and in the CR are expected to
remain below 120 F during Phase 1 of an ELAP event (approximately 8 hours).
Therefore, the temperatures in the battery rooms above and below the CR are
expected to be approximately the same as the temperatures of the ESGR and
the CR, respectively, during Phase 1.
The FSG procedures for Phase 2 require the battery room exhaust flow path and
exhaust fans to be aligned and flow confirmed prior to starting the battery
chargers, which are powered by the 480 VAC portable diesel generators. The
exhaust fans and exhaust flow paths are the same components used in normal
plant operation and design basis events. As previously stated, the two battery
rooms located above the CR take suction from the CR and the two battery rooms
located below the CR take suction from the ESGR. Calculation ME-0972, Rev. 0
shows that the expected loss of ventilation transient temperatures in the sources
of suction for the battery room ventilation systems (i.e., the ESGR and CR) are
expected to remain below 120 F indefinitely.
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Although the Phase 2 conditions in the battery rooms are acceptable indefinitely,
the current strategy for Phase 3 is to repower a CR chiller for each unit and thus
re-establish normal HVAC cooling capacity for the CR envelope. The completed
ventilation strategy (OIP Open Item #13) will be provided in the February 2014
Six-Month Status Update.
The impact of extreme low temperatures is not expected to be significant due to
the continuous connection with the CR and ESGR spaces and the heat storage
capacity of the battery room concrete walls/floors/ceilings. However, if
decreasing battery room temperatures become a concern, the FSG procedures
provide for the use of portable heating equipment.
Since battery rooms are not modeled in the loss of ventilation transient analysis model, it
appears that there is no analysis or calculation to demonstrate the adequacy of the battery room
ventilation. This is identified as Confirmatory Item 3.2.4.2.B in Section 4.2.
During audit, the licensee was requested to provide a detailed summary of the analysis and/or
technical evaluation performed to demonstrate the adequacy of the ventilation provided in the
TDAFW pump room to support equipment operation throughout all phases of an ELAP.
In response, the licensee stated:
Calculation 01040.4410-USB-268, Rev 0, “SBO Loss of Ventilation Temperature
Transients,” was reviewed and indicates that after 8 hours the TDAFW pump
room temperature remains below approximately 129 F. The SBO calculations
are conservative, since they do not credit all the heat sink areas, or opening
doors and dampers. The calculations also do not credit diurnal swings in outside
air temperatures. All of these factors would tend to reduce the temperature
inside the TDAFW pump room. Since the TDAFW pump is expected to operate
during Phase 1, Phase 2 and Phase 3 of an ELAP event and the potential exists
for temperatures to slowly rise beyond the value evaluated at 8 hours, FSG
procedures will direct the opening of the exterior access door and/or blocking
open the wall dampers to maintain the room at or below the maximum calculated
transient temperature (129 F) determined by the SBO Loss of Ventilation
calculation identified above.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01 and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to ventilation equipment cooling, if
these requirements are implemented as described.
3.2.4.3 Heat Tracing
NEI 12-06, Section 3.2.2, Guideline (12) states:
Plant procedures/guidance should consider loss of heat tracing effects for
equipment required to cope with an ELAP. Alternate steps, if needed, should be
identified to supplement planned action.
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Heat tracing is used at some plants to ensure cold weather conditions do not
result in freezing important piping and instrumentation systems with small
diameter piping. Procedures/guidance should be reviewed to identify if any heat
traced systems are relied upon to cope with an ELAP. For example, additional
condensate makeup may be supplied from a system exposed to cold weather
where heat tracing is needed to ensure control systems are available. If any
such systems are identified, additional backup sources of water not dependent
on heat tracing should be identified.
In the Integrated Plan, the licensee did not address the loss of heat tracing. The licensee
screened in for extreme cold, ice and snow and therefore the licensee should address loss of
heat tracing effects on FLEX strategies.
During the audit, the licensee was requested to provide a discussion on the effects of the loss of
heat tracing in regards to the effects for equipment required to cope with an ELAP, including
alternate steps, if needed, to supplement planned actions.
In response to the audit, the licensee stated that heat trace is used to provide two protection
functions:
1. Heat trace is used to maintain highly concentrated soluble boron solutions above
the temperature where the soluble boron will precipitate out of solution.
2. Heat trace is also used to protect piping systems and components from freezing
in extreme cold weather conditions.
The licensee stated that the FLEX strategies developed do not depend on highly concentrated
soluble boron solutions and the FLEX strategies developed will use borated water sources with
boron concentrations below 4000 PPM. The licensee stated that at these levels boron
precipitation is not expected to occur. The licensee further stated that in addition, FLEX
strategies for the mixing of borated water in portable FLEX tanks includes equipment such as an
agitator and a tank heater to facilitate complete dissolution of the boric acid crystals. The
licensee stated that the FLEX strategies will provide guidance for mixing to maintain
concentrations below the solubility limit corresponding to freezing temperatures, which will
ensure that boron precipitation at low ambient temperatures is not challenged.
The licensee stated that FLEX strategies have been developed to protect piping systems and
components from freezing. The licensee stated that commercially available heat tape and
insulation rolls have been identified and will be procured and maintained in the FLEX Storage
Building for use on piping systems and components that will be used during an ELAP event
where freezing is a concern in extreme cold weather conditions. The licensee stated that major
components being procured for FLEX strategies will be provided with cold weather packages
and small electrical generators to power the heat tape circuits as well as protect the equipment
from damage due to extreme cold weather and help assure equipment reliability. In addition,
the licensee stated that the CST level instrument tubing credited for BDB and subject to freezing
conditions in an ELAP, will be protected with the use of heat lamps which can be powered from
small generators that have been procured for FLEX strategies or from the small generators that
will be included as part of the large BDB pump skids being purchased.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
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assurance that the requirements of Order EA-12-049 will be met with respect to heat tracing, if
these requirements are implemented as described.
3.2.4.4 Accessibility – Lighting and Communications
NEI 12-06, Section 3.2.2, Guideline (8) states:
Plant procedures/guidance should identify the portable lighting (e.g., flashlights
or headlamps) and communications systems necessary for ingress and egress to
plant areas required for deployment of FLEX strategies.
Areas requiring access for instrumentation monitoring or equipment operation
may require portable lighting as necessary to perform essential functions.
Normal communications may be lost or hampered during an ELAP.
Consequently, in some cases, portable communication devices may be required
to support interaction between personnel in the plant and those providing overall
command and control.
On page 78 of the Integrated Plan, the licensee stated that the FLEX strategies for Phase 1 for
maintenance and/or support of safety functions involve several elements. One necessary
element is maintaining sufficient lighting in areas needed to successfully implement the planned
FLEX strategies. North Anna Power Station initially relies on emergency lighting installed for
Fire Protection/Appendix R to perform Phase 1 coping strategy activities. However, Appendix R
lighting is powered by battery packs at each light and is rated for only 8 hours. This lighting also
does not provide a100% coverage of areas involving FLEX strategy activities including ingress
and egress from task areas. In these areas and areas poorly lit, portable lighting and
headlamps are available for use. Portable lighting is currently staged throughout the site,
mainly for use by the Fire Brigade or Appendix R fire response.
On page 80 of the Integrated Plan, the licensee stated that the FLEX strategies for Phase 2
involves three methods of providing light in areas needed to successfully implement FLEX
strategies. The first method is the continued use of the Appendix R lighting discussed above.
However, as previously stated this lighting is limited to approximately 8 hours. The second
method is the use of supplemental lights that will be available as stored BDB equipment. This
includes additional small portable sources (e.g., flashlights and head lamps) for personal uses,
as well as larger portable equipment (e.g., self-powered light plants). The larger lighting
equipment would be typically deployed in outside areas to support deployment of BDB pumps
and generators. In some cases, BDB equipment will be equipped with their independent lighting
sources. The third method is the restoration of power to various lighting panels in the electrical
distribution system. A lighting study will be performed to validate the adequacy of supplemental
lighting and the adequacy and practicality of using portable lighting to perform FLEX strategy
actions. This is being tracked by licensee Open Item 17. This is identified as Confirmatory Item
3.2.4.4.A in Section 4.2 below.
During audit, the licensee was requested to clarify the means of communication between the
control room and local equipment operators for the SG makeup pumps (i.e., TDAFW or FLEX
pumps) and ADVs to affect a symmetric cooldown of the RCS. The licensee was further
requested to clarify whether environmental factors such as elevated temperatures or ambient
noise of exiting steam have been considered in the evaluation to determine that the necessary
coordination is feasible.
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In response, the licensee stated:
There are multiple communication strategies available to the operating staff.
During the first couple of hours of an ELAP event the station’s Public Address
(PA) system (powered from the station vital 120 VAC Bus) is expected to remain
available. Following load stripping actions the PA system would become
unavailable and the staff would then rely on BDB hand-held analog radios or on
the site sound-powered phone circuits. Neither of these options relies on
electrical power, however the hand-held radios are powered by rechargeable
batteries. Spare batteries will be available and the FLEX strategy includes
provisions to provide portable generators to power the various battery chargers.
Should the analog radios experience difficulty with reception signal strength the
staff would rely on the sound- powered phones circuits that are permanently
installed throughout the plant.
In high noise areas, the sound-powered phone circuits will provide the preferred
communication strategies since the head sets on these phones provide
significant noise dampening attributes. Multiple phone circuits are available in
the BDB response areas and the ability to cross-tie the phone circuits provides
additional flexibility. BDB dedicated sound-powered headsets are being
purchased as part of the FLEX strategies.
Temperatures in the Main Steam Valve House (MSVH) where the atmospheric
dump valves (SG PORVs) would be locally manually operated have been
evaluated and determined to remain in the normal operating range. Normal plant
practices for accessing this area during full power operation would be employed
in the event of an ELAP.
Therefore, local temperatures and high noise have been considered and
communications with operators is expected to be effective and coordination of
activities feasible.
The NRC staff has reviewed the licensee communications assessment (ML12307A028 and
ML13064A012) in response to the March 12, 2012 50.54(f) request for information letter for
North Anna and, as documented in the staff analysis (ML13114A067) has determined that the
assessment for communications is reasonable, and the analyzed existing systems, proposed
enhancements, and interim measures will help to ensure that communications are
maintained. Therefore, there is reasonable assurance that the guidance and strategies
developed by the licensee will conform to the guidance of NEI 12-06 Section 3.2.2 (8) regarding
communications capabilities during an ELAP. This is identified as Confirmatory Item 3.2.4.4.B
in Section 4.2 below.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01 and subject to the successful
closure of issues related to the Confirmatory Items, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to lighting and portable
communications, if these requirements are implemented as described.
3.2.4.5 Protected and Internal Locked Area Access
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NEI 12-06, Section 3.2.2, Guideline (9) states:
Plant procedures/guidance should consider the effects of ac power loss on area
access, as well as the need to gain entry to the Protected Area and internal
locked areas where remote equipment operation is necessary.
At some plants, the security system may be adversely affected by the loss of the
preferred or Class 1E power supplies in an ELAP. In such cases, manual actions
specified in ELAP response procedures/guidance may require additional actions
to obtain access.
On page 98 of the Integrated Plan, the licensee stated:
The FLEX strategies for maintenance and/or support of safety functions involve
several elements. One element is the ability to access site areas required for
successful implementation of the planned FLEX strategy.
The potential impairments to required access are doors and gates. The coping
strategy to maintain site accessibility through doors and gates is applicable to all
phases of the FLEX coping strategies, but is immediately required as part of
Phase 1. Doors and gates serve a variety of barrier functions on the site. One
primary function is security and is discussed below. However, other barrier
functions include fire, flood, radiation, ventilation, tornado, and high energy line
break (HELB). As barriers, these doors and gates are typically administratively
controlled to maintain their function as barriers during normal operations.
Following an ELAP event, FLEX coping strategies require the routing of hoses
and cables to be run through various barriers in order to connect BDB equipment
to station fluid and electric systems. For this reason, certain barriers (gates and
doors) will be opened and remain open under administrative control.
The security doors and gates of concern are those barriers that rely on electric
power to operate opening and/or locking mechanisms. The ability to open doors
for ingress and egress, ventilation, or temporary cables/hoses routing is
necessary to implement the FLEX coping strategies. The Security force will
initiate an access contingency upon loss of the Security Diesel and all AC/DC
power as part of the Security Plan. Access to the Owner Controlled Area, site
Protected Area, and areas within the plant structures will be controlled under this
access contingency.
Vehicle access to the Protected Area is via the double gated sally-port at the
Security Building. As part of the Security access contingency, the sally-port
gates will be manually controlled to allow delivery of BDB equipment (e.g.,
generators, pumps) and other vehicles such as debris removal equipment into
the Protected Area.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to protected and
internal locked area access, if these requirements are implemented as described.
3.2.4.6 Personnel Habitability – Elevated Temperature
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NEI 12-06, Section 3.2.2, Guideline (11), states:
Plant procedures/guidance should consider accessibility requirements at locations
where operators will be required to perform local manual operations.
Due to elevated temperatures and humidity in some locations where local
operator actions are required (e.g., manual valve manipulations, equipment
connections, etc.), procedures/guidance should identify the protective clothing or
other equipment or actions necessary to protect the operator, as appropriate.
FLEX strategies must be capable of execution under the adverse conditions
(unavailability of installed plant lighting, ventilation, etc.) expected following a
BDBE resulting in an ELAP/LUHS. Accessibility of equipment, tooling, connection
points, and plant components shall be accounted for in the development of the
FLEX strategies. The use of appropriate human performance aids (e.g.,
component marking, connection schematics, installation sketches, photographs,
etc.) shall be included in the FLEX guidance implementing the FLEX strategies.
Section 9.2 of NEI 12-06 states,
Virtually every state in the lower 48 contiguous United States has experienced
temperatures in excess of 110°F. Many states have experienced temperatures
in excess of 120°F.
On page 91 of the Integrated Plan, the licensee stated that the FLEX strategies for maintenance
and/or support of safety functions involve several elements. One element is to ensure that
ventilation, heating, and cooling is adequate to maintain acceptable environmental conditions for
equipment operation and personnel habitability. In the six-month update (Item #13) and during
the audit process, the licensee stated that the finalized details of the ventilation strategy are still
under development and will conform to the guidance given in NEI 12-06. The details of this
strategy will be provided at a later date. This is included as part of Confirmatory Item 3.2.4.2.A
in Section 4.2 below.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01 and subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to personnel habitability - elevated
temperature, if these requirements are implemented as described.
3.2.4.7 Water Sources.
NEI 12-06, Section 3.2.2, Guideline (5) states:
Plant procedures/guidance should ensure that a flow path is promptly established
for makeup flow to the steam generator/nuclear boiler and identify backup water
sources in order of intended use. Additionally, plant procedures/guidance should
specify clear criteria for transferring to the next preferred source of water.
Under certain beyond-design-basis conditions, the integrity of some water
sources may be challenged. Coping with an ELAP/LUHS may require water
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supplies for multiple days. Guidance should address alternate water sources
and water delivery systems to support the extended coping duration. Cooling
and makeup water inventories contained in systems or structures with designs
that are robust with respect to seismic events, floods, and high winds, and
associated missiles are assumed to be available in an ELAP/UHS at their
nominal capacities. Water in robust UHS piping may also be available for use
but would need to be evaluated to ensure adequate NPSH can be demonstrated
and, for example, that the water does not gravity drain back to the UHS.
Alternate water delivery systems can be considered available on a case-by-case
basis. In general, all CSTs should be used first if available. If the normal source
of makeup water (e.g., CST) fails or becomes exhausted as a result of the
hazard, then robust demineralized, raw, or borated water tanks may be used as
appropriate.
Heated torus water can be relied upon if sufficient [net positive suction head]
NPSH can be established. Finally, when all other preferred water sources have
been depleted, lower water quality sources may be pumped as makeup flow
using available equipment (e.g., a diesel driven fire pump or a portable pump
drawing from a raw water source). Procedures/guidance should clearly specify
the conditions when the operator is expected to resort to increasingly impure
water sources.
On page 23 of the Integrated Plan, the licensee stated that initially, AFW water supply will be
provided by the installed emergency condensate storage tank (ECST). The tank has a minimum
usable capacity of 96,649 gallons and will provide a suction source to the TDAFW pump for a
minimum of 3.8 hours of RCS decay heat removal assuming a concurrent RCS cooldown at
100°F/hr to a minimum SG pressure of 290 psig. After depletion of the inventory in the ECST,
the TDAFW pump suction will be aligned to the fire protection (FP) system. The FP system will
be pressurized by the diesel driven fire pump (DDFP), which provides water from the Service
Water Reservoir at sufficient flowrate and pressure to support TDAFW pump operation. The
Service Water Reservoir provides an approximately 22.5 million gallon useable water volume to
the FP system since the service water system would not be functional due to the ELAP/LUHS..
Potential debris at the suction screening of the DDFP would not prevent an adequate flow to the
DDFP. The trash screens on the SW reservoir intake bay are designed to pass the full design
flow of a SW pump and the FP pump. The SW pumps will not be operating due to the
ELAP/LUHS. Since the 600 gpm required by the DDFP to provide a suction source for the
TDAFW pump is a small fraction of the design flow rate of the trash screen, the calculated
unblocked trash screen area required for passing the required flow rate is justifiable.
On page 26 of the Integrated Plan, the licensee stated that a back-up indefinite supply of water,
as make-up to the ECST or directly to the suction of the portable diesel driven BDB AFW pump,
can be provided from Lake Anna or the Service Water Reservoir. Lake Anna and the Service
Water Reservoir will remain available for any of the external hazards applicable to North Anna.
The portable, diesel driven BDB High Capacity pump will be transported from the BDB Storage
Building(s) to a location near the selected water source. A flexible hose will be routed from the
pump suction to the water source where water will be drawn through a strainer sized to limit
solid debris size to prevent damage to the TDAFW or the BDB AFW pump. A flexible hose will
be routed from the BDB High Capacity Pump discharge to the BDB ECST refill connection or to
the suction of the portable BDB AFW pump.
In the 6-month update to the Integrated Plan, dated April 30, 2013, the licensee stated that
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changes to the timing of the RCS injection strategy have been made. The strategy for RCS
injection for inventory and reactivity control has been moved from a Phase 3 activity to a Phase
2 activity. North Anna will purchase and store BDB RCS Injection Pumps for use in the Phase 2
RCS Inventory strategy. The RCS injection strategy supplies make-up water to the RCS from
either units RWST or from a portable borax acid mixing tank, which would be filled using the
BDB B AFW pump or the BDB high capacity pump taking suction from Lake Anna.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to water sources,
if these requirements are implemented as described.
3.2.4.8 Electrical Power Sources/Isolations and Interactions.
NEI 12-06, Section 3.2.2, Guideline (13) states in part:
The use of portable equipment to charge batteries or locally energize equipment
may be needed under ELAP/LUHS conditions. Appropriate electrical isolations
and interactions should be addressed in procedures/guidance.
On page 63 of the Integrated Plan, the licensee stated that prior to depletion of the Class lE 125
V DC batteries, vital 120 VAC circuits will be re-powered to continue to provide key parameter
monitoring instrumentation using portable diesel generators (DGs) stored on-site. In addition,
selected plant lighting will be re-energized.
During the audit, the licensee was requested to provide single-line diagrams showing the
proposed connections of Phase 2 and 3 electrical equipment on the e-Portal, to include
protection information (breaker, relay, etc.) and rating of the equipment on the Single Line
Diagrams. In response, the licensee stated that Figure 7 in the Integrated Plan provides a
Single Line Diagram for North Anna showing the proposed connections for the Phase 2 and 3
diesel generators. (A revised Figure 7 was provided in the August 2013 six-month status
update.) Additional details regarding protection information for the North Anna emergency
buses is available in the North Anna Drawings for Unit 1 & Unit 2 (11715/12050 –FE-1BA),
“Protective Device Coordination Electrical One Line Diagram.”
During the audit, the licensee was requested to provide a summary of the sizing calculation for
the FLEX generators to show that they can supply the loads assumed in phases 2 and 3.
In response, the licensee stated that for Unit 1, Calculation EE-0863, “Calculation for North
Anna Power Station Beyond Design Basis – FLEX Electrical 480VAC and 120VAC System
Loading Analysis for NAPS BDB FLEX DC NA-13-01017” provides the basis for the sizing of the
North Anna Phase 2 portable BDB diesel generators. For Unit 1, the total loads for the 120
VAC and 480 VAC DGs are 12.4 kW and 189 kW, respectively. The calculation for Unit 2 is
Calculation EE-0865, “Calculation for North Anna Power Station Beyond Design Basis – FLEX
Electrical 480VAC and 120VAC System Loading Analysis for NAPS BDB FLEX DC NA-1301018." Additional details for the individual 120 VAC and 480 VAC loads for Unit 2 are provided
in Attachment 13.1 of the Calculation EE-0865. The sizes of the 120 VAC and 480 VAC BDB
diesel generators are 35.5 kW and 350 kW, respectively.
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The licensee further stated that the Phase 3 4160 VAC BDB diesel generator loading analysis
has not been completed. It is estimated that the total loads for either unit will be approximately
1.7 MW. The portable diesel generators available from the RRC will be 2 MW generators.
The licensee further stated that as provided in the North Anna six-month status update, dated
August 23, 2013, the scheduled completion date for the calculations documenting the
load/sizing analyses was extended to December 2013. Calculations EE-0863 and EE-0865
discussed above for the 120 VAC and 480 VAC loads for Units 1 and 2, respectively, have been
completed. The 4160 VAC load/sizing calculation will be completed in December 2013. This is
identified as Confirmatory Item 3.2.4.8.A in Section 4.2 below.
During the audit, the licensee was requested to describe how electrical isolation will be
maintained such that (a) Class 1E equipment is protected from faults in portable/FLEX
equipment and (b) multiple sources do not attempt to power electrical buses.
In response, the licensee stated that for permanently installed BDB equipment connections, the
connection hardware is either procured/installed to the requirements of safety related equipment
or is isolated from the class IE buses in accordance with the approved license basis for each
unit. The FSGs provide guidance for energizing a Class 1E bus using portable generators
consistent with NEI 12-06, Section 3.2.2. The BDB portable diesel generators will be used only
when the Class 1E Diesel Generators have been isolated. Each of the BDB portable diesel
generators will be provided with output electrical protection (breakers, fuses, relays, etc.) that
will provide protection for the output cables and the connection buses. Existing load circuit
protection will be used for the bus loads. Class 1E equipment is protected by existing protection
relaying. FLEX strategy does not change any existing equipment protection scheme.
Electrical isolation to prevent simultaneously supplying power to the same bus from different
sources will be administratively controlled. The FSGs will be written to ensure the breakers
from other potential supply sources are racked out and tagged before power is supplied to the
bus by use of a BDB portable diesel generator which will be connected directly to the
emergency bus for the 4160 VAC tie-in and to permanently installed receptacles for the 480
VAC tie-in.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and subject to the successful
closure of issues related to the Confirmatory Items, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to electrical power sources/isolations
and interactions, if these requirements are implemented as described.
3.2.4.9 Portable Equipment Fuel.
NEI 12-06, Section 3.2.2, Guideline (13) states in part:
The fuel necessary to operate the FLEX equipment needs to be assessed in the
plant specific analysis to ensure sufficient quantities are available as well as to
address delivery capabilities.
NEI 12-06, Section 3.2.1.3, initial condition (5) states:
Fuel for FLEX equipment stored in structures with designs which are robust with
respect to seismic events, floods and high winds and associated missiles,
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remains available.
On page 70 of the Integrated Plan, the licensee stated that the general coping strategy for
supplying fuel oil to diesel driven portable equipment used to cope with an ELAP / LUHS, is to
draw fuel oil out of any available existing diesel fuel oil tanks on the North Anna site. During
Phase 1, the only fuel requirements would be to re-fuel the diesel driven fire pumps which has
an 8 hour fuel oil supply at the beginning of the ELAP event. However, no fuel is required for
stored or staged BDB equipment for any of the Phase 1 coping strategies.
On Page 72 of the Integrated Plan, the licensee stated that, for Phase 2 and Phase 3 the
primary source of fuel oil for portable equipment will be the EDG Fuel Oil Day Tanks. These four
diesel tanks contain 800 gallons of diesel fuel each (a total of 3200 gallons) and are seismically
mounted and housed in the tornado protected EDG rooms. The licensee stated that, fuel can be
obtained using the tank drain valve and a flexible hose; fuel can be gravity fed to suitable fuel
containers for transport to BDB equipment so no pumps are necessary.
The licensee stated that a secondary source for fuel oil will be the two EDG Underground Diesel
Fuel Oil Storage Tanks. Each tank has a 45,000 gallon capacity. These tanks are protected
from high winds, tornado missiles, seismic events, and floods. The licensee stated that fuel can
be obtained using a cart mounted 12 VDC fuel pump and attaching the pump suction to any of
the eight (8) EDG fuel transfer pump suction strainer drain valves and pumping the fuel oil to
suitable fuel containers for transport. The licensee stated that fuel transfer carts and pumps are
stored in the BDB Storage Building(s).
The licensee stated that an evaluation of all BDB equipment fuel consumption and required refill strategies will be developed including any gasoline required for small miscellaneous
equipment. The licensee stated that site-specific procedural guidance governing re-fueling
strategies will be developed using industry guidance, and will address the monitoring of fuel
supplies and consumption in order to initiate refueling activities prior to FLEX equipment
shutdown (including the diesel-driven fire pump at the SW reservoir. The licensee does not
discuss how the quality fuel oil and gasoline supplies will be controlled in order to ensure proper
diesel or gasoline-powered FLEX equipment operation. In addition the licensee did not discuss
available sources of gasoline and how those sources will be protected to ensure availability
following a BDB event. This is identified as Confirmatory Item 3.2.4.9.A in Section 4.2 below
On page 76 of the Integrated Plan, the licensee stated that, for Phase 3, the coping strategy for
supplying fuel oil to diesel driven portable equipment is the same as described for Phase 2. The
licensee stated that the fuel strategy will evaluate the need for additional fuel required from the
RRC or other offsite sources. However, the licensee does not describe how the onsite fuel
capacity provides an indefinite supply of fuel or if the RRC is capable of providing an indefinite,
ongoing supply of fuel. This is included with Confirmatory Item 3.2.4.9.A in Section 4.2 below.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and, subject to the successful
closure of issues related to the Confirmatory Item, provides reasonable assurance that the
requirements of Order EA-12-049 will be met with respect to portable equipment fuel, if these
requirements are implemented as described.
3.2.4.10 Load Reduction to Conserve DC Power.
NEI 12-06, Section 3.2.2, Guideline (6) states:
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Plant procedures/guidance should identify loads that need to be stripped from the
plant dc buses (both Class 1E and non-Class 1E) for the purpose of conserving
dc power.
DC power is needed in an ELAP for such loads as shutdown system
instrumentation, control systems, and dc backed AOVs and MOVs. Emergency
lighting may also be powered by safety-related batteries. However, for many
plants, this lighting may have been supplemented by Appendix R and security
lights, thereby allowing the emergency lighting load to be eliminated. ELAP
procedures/guidance should direct operators to conserve dc power during the
event by stripping nonessential loads as soon as practical. Early load stripping
can significantly extend the availability of the unit’s Class 1E batteries. In certain
circumstances, AFW/HPCI /RCIC operation may be extended by throttling flow to
a constant rate, rather than by stroking valves in open-shut cycles.
Given the beyond-design-basis nature of these conditions, it is acceptable to strip
loads down to the minimum equipment necessary and one set of instrument
channels for required indications. Credit for load-shedding actions should
consider the other concurrent actions that may be required in such a condition.
On page 10 of the Integrated Plan, the licensee stated that plant specific analysis for extension
of Class 1E DC battery life included an initial condition that load stripping would be completed in
90 minutes from an ELAP event. The licensee stated that, with completion of load stripping in
90 minutes, the battery life was calculated as 8 hours for Unit 1 and 8 hours for Unit 2. Within
60 minutes of the initiating event, an ELAP condition would be diagnosed and load stripping of
the vital buses would be initiated. Load stripping starts at 60 minutes from the initiating event
and is completed within 30 minutes. The vital 120 VAC panels and 125 VDC panels required to
be accessed by the operator to perform load stripping are located either in the Main Control
Room (MCR) or directly below in the Emergency Switchgear Room (ESGR). The licensee
stated that because the panels are readily accessible (close proximity to the normal duty station
for the operator assigned this action) and load stripping is an uncomplicated task, completing
the load stripping action within 30 minutes is reasonable. Therefore the 90 minute time
constraint can be met.
During the audit, the licensee was requested to provide the dc load profile with the required
loads for the mitigating strategies to maintain core cooling, containment, and spent fuel pool
cooling.
In response, the licensee stated that Calculation EE-0009, Rev. 1, Addendum J, “125V DC
System Analysis,” Attachment 15.5, Pages 1 thru 8, provides the dc load profile with the
required loads for the North Anna FLEX mitigating strategies.
During the audit, the licensee was requested to provide a detailed discussion on the loads that
will be shed from the dc bus, the equipment location (or location where the required action
needs to be taken), and the required operator actions needed to be performed and the time to
complete each action.
In response, the licensee stated that there are four (4) 125 VDC buses at North Anna. The four
dc bus distribution panels are located in the ESGR at elevation 254', directly below the MCR at
elevation 274'. The ESGR has multiple access points including the stairwell behind the MCR,
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two access points from elevation 254' in the turbine building, and the control rod drive room.
The ESGR is a part of the MCR pressure envelope and is in a Category 1 turbine-missile and
flood protected room. Multiple access points provide reasonable assurance that the 125 VDC
panels will remain accessible during any BDB ELAP scenario.
The licensee stated that, upon declaration of an ELAP, an operator will be dispatched from the
MCR to perform dc bus load stripping per the guidance in FSG-4, “ELAP DC Bus Load Shed
and Management." Within 60 minutes after an ELAP event, the guidance instructs the operator
to secure the dc-powered seal oil pump and dc-powered turbine oil pump, after ensuring the
hydrogen gas has been vented from the main generators. The licensee stated that once the
pumps have been secured, the operator will then strip the remaining dc loads from the dc buses
and the ac loads from the vital buses within the following 30 minutes; all load stripping will be
completed within 90 minutes following initiation of the event.
The licensee stated that the four dc buses each provide power to their respective vital bus
inverters, which convert 125 VDC to 120 VAC. The loads are stripped from the dc busses with
the exception of these vital bus inverters. Load stripping in FSG-4 also includes the guidance to
strip selected 120 VAC vital bus loads to preserve the emergency batteries. The required
actions to strip the 120 VAC loads from the AC buses are performed in the Hathaway and
Computer Rooms, which are an extension of the MCR, elevation 274’ Tables provided in FSG-4
give the operators a detailed description of the vital bus ac and the dc loads that will be required
to be stripped and the basis for stripping the load. The operator guide tables are provided for
Unit 1 and are typical for Unit 2.
The licensee stated that, Per NEI 12-06, Section 3.2.1.3(9), FLEX strategies do not need to
assume additional failures beyond those attributed to the BDB External Event directly, and as
such instrumentation redundancy is not a requirement for the key parameter indications, which
remain available after load-stripping has been performed. However, as a defense in depth
approach, the licensee stated that alternate indication is available from an independent source
(e.g. a local pressure gauge, level versus flow indication, etc.) for many of the North Anna key
parameters identified in the Integrated Plan.
During the audit, the licensee was requested to provide the basis for the minimum dc bus
voltage that is required to ensure proper operation of all required electrical equipment.
In response, the licensee stated that the basis for the final 1E battery terminal voltage is the
design minimum voltage per cell given in North Anna stationary battery specification NAS-2050.
Section 2.1.3, of NAS-2050, “General Technical Requirements” states that the minimum voltage
per cell for a Class 1E battery is 1.75 VDC per cell. Since North Anna utilizes a 60 cell battery,
the final Class 1E battery terminal voltage is 105 VDC (60 x 1.75VDC).
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01, and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to load reduction
to conserve DC power, if these requirements are implemented as described.
3.3
PROGRAMMATIC CONTROLS
3.3.1 Equipment Maintenance and Testing.
NEI 12-06, Section 3.2.2, following item (15) states:
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In order to assure reliability and availability of the FLEX equipment required to
meet these capabilities, the site should have sufficient equipment to address all
functions at all units on-site, plus one additional spare, i.e., an N+1 capability,
where “N” is the number of units on-site. Thus, a two-unit site would nominally
have at least three portable pumps, three sets of portable ac/dc power supplies,
three sets of hoses & cables, etc. It is also acceptable to have a single resource
that is sized to support the required functions for multiple units at a site (e.g., a
single pump capable of all water supply functions for a dual unit site). In this
case, the N+1 could simply involve a second pump of equivalent capability. In
addition, it is also acceptable to have multiple strategies to accomplish a function
(e.g., two separate means to repower instrumentation). In this case the
equipment associated with each strategy does not require N+1. The existing
50.54(hh)(2) pump and supplies can be counted toward the N+1, provided it
meets the functional and storage requirements outlined in this guide. The N+1
capability applies to the portable FLEX equipment described in Tables 3-1 and
3-2 (i.e., that equipment that directly supports maintenance of the key safety
functions). Other FLEX support equipment only requires an N capability.
NEI 12-06, Section 11.5 states:
1. FLEX mitigation equipment should be initially tested or other reasonable
means used to verify performance conforms to the limiting FLEX
requirements. Validation of source manufacturer quality is not required.
2. Portable equipment that directly performs a FLEX mitigation strategy for the
core, containment, or SFP should be subject to maintenance and testing1
guidance provided in INPO AP 913, Equipment Reliability Process, to verify
proper function. The maintenance program should ensure that the FLEX
equipment reliability is being achieved. Standard industry templates (e.g.,
EPRI) and associated bases will be developed to define specific maintenance
and testing including the following:
a. Periodic testing and frequency should be determined based on equipment
type and expected use. Testing should be done to verify design
requirements and/or basis. The basis should be documented and
deviations from vendor recommendations and applicable standards
should be justified.
b. Preventive maintenance should be determined based on equipment type
and expected use. The basis should be documented and deviations from
vendor recommendations and applicable standards should be justified.
c. Existing work control processes may be used to control maintenance and
testing. (e.g., PM Program, Surveillance Program, Vendor Contracts, and
work orders).
1
Testing includes surveillances, inspections, etc.
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3. The unavailability of equipment and applicable connections that directly
performs a FLEX mitigation strategy for core, containment, and SFP should
be managed such that risk to mitigating strategy capability is minimized.
a. The unavailability of installed plant equipment is controlled by existing
plant processes such as the Technical Specifications. When installed
plant equipment which supports FLEX strategies becomes unavailable,
then the FLEX strategy affected by this unavailability does not need to be
maintained during the unavailability.
b. Portable equipment may be unavailable for 90 days provided that the site
FLEX capability (N) is available.
c. Connections to permanent equipment required for FLEX strategies can
be unavailable for 90 days provided alternate capabilities remain
functional.
d. Portable equipment that is expected to be unavailable for more than 90
days or expected to be unavailable during forecast site specific external
events (e.g., hurricane) should be supplemented with alternate suitable
equipment.
e. The short duration of equipment unavailability, discussed above, does not
constitute a loss of reasonable protection from a diverse storage location
protection strategy perspective.
f.
If portable equipment becomes unavailable such that the site FLEX
capability (N) is not maintained, initiate actions within 24 hours to restore
the site FLEX capability (N) and implement compensatory measures
(e.g., use of alternate suitable equipment or supplemental personnel)
within 72 hours.
The generic concern involving clarification of how licensees would maintain FLEX equipment
such that it would be readily available for use is applicable to North Anna. This generic concern
has been resolved generically through the NRC endorsement of the EPRI technical report on
preventive maintenance of FLEX equipment, submitted by NEI by letter dated October 3, 2013
(ADAMS Accession No. ML13276A573). The endorsement letter from the NRC staff is dated
October 7, 2013 (ADAMS Accession No. ML13276A224).
This Generic Concern involves clarification of how licensees would maintain FLEX equipment
such that it would be readily available for use. The technical report provided sufficient basis to
resolve this concern by describing a database that licensees could use to develop preventative
maintenance programs for FLEX equipment. The database describes maintenance tasks and
maintenance intervals that have been evaluated as sufficient to provide for the readiness of the
FLEX equipment. The NRC staff has determined that the technical report provides an
acceptable approach for maintaining FLEX equipment in a ready-to-use status.
During the audit, the licensee stated that the EPRI Templates will be used for most equipment.
However, in the event that EPRI templates are not available, Preventative Maintenance (PM)
actions will be developed based on manufacturer provided information/recommendations.
Additionally, EPRI Templates will be adopted for new pieces of FLEX equipment as they are
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purchased/received on site.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01 and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to maintenance
and testing, if these requirements are implemented as described.
3.3.2 Configuration Control.
NEI 12-06, Section 11.8 states:
1. The FLEX strategies and basis will be maintained in an overall program
document. This program document will also contain a historical record of
previous strategies and the basis for changes. The document will also contain
the basis for the ongoing maintenance and testing programs chosen for the
FLEX equipment.
2. Existing plant configuration control procedures will be modified to ensure that
changes to the plant design, physical plant layout, roads, buildings, and
miscellaneous structures will not adversely impact the approved FLEX
strategies.
3. Changes to FLEX strategies may be made without prior NRC approval
provided:
a) The revised FLEX strategy meets the requirements of this guideline.
b) An engineering basis is documented that ensures that the change in
FLEX strategy continues to ensure the key safety functions (core and
SFP cooling, containment integrity) are met.
On page 19 of the Integrated Plan, the licensee stated that the FLEX strategies and their bases
will be maintained in an overall program document. The program document will address the key
safety functions to provide reactor core cooling and heat removal, provide RCS inventory and
reactivity control, ensure containment integrity, provide spent fuel pool cooling, provide
indication of key parameters, and provide reactor core cooling (Modes 5 and 6).
The licensee stated that support functions for the implementation of the FLEX strategies include
providing load stripping of 125 VDC and 120 VAC vital buses to extend battery life, re-powering
AC and DC electrical buses, providing ventilation for equipment cooling and area habitability,
providing lighting, providing communications capability, providing for fueling of portable
equipment, and providing plant and area access. The licensee stated that the program
document will contain a historical record of previous strategies and their bases. In addition, the
program document will include the bases for ongoing maintenance and testing activities for the
BDB equipment.
The licensee stated that existing design control procedures will be modified to ensure that
changes to the plant design, physical plant layout, roads, buildings, and miscellaneous
structures will not adversely impact the approved FLEX strategies. Changes for the FLEX
strategies will be reviewed with respect to operations critical documents to ensure no adverse
effect. The licensee stated that, future changes to the FLEX strategies may be made without
prior NRC approval provided that the revised FLEX strategies meet the requirements of NEI 1206. The licensee stated that an engineering basis will be documented that ensures that the
change in FLEX strategies continues to ensure the key safety functions (core and SFP cooling,
containment integrity) are met.
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The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01 and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to configuration
control, if these requirements are implemented as described.
3.3.3 Training.
NEI 12-06, Section 11.6 provides that:
1. Programs and controls should be established to assure personnel proficiency
in the mitigation of beyond-design-basis events is developed and maintained.
These programs and controls should be implemented in accordance with an
accepted training process.2
2. Periodic training should be provided to site emergency response leaders3 on
beyond design-basis emergency response strategies and implementing
guidelines. Operator training for beyond-design-basis event accident
mitigation should not be given undue weight in comparison with other training
requirements. The testing/evaluation of Operator knowledge and skills in this
area should be similarly weighted.
3. Personnel assigned to direct the execution of mitigation strategies for
beyond-design basis events will receive necessary training to ensure
familiarity with the associated tasks, considering available job aids,
instructions, and mitigating strategy time constraints.
4. “ANSI/ANS 3.5, Nuclear Power Plant Simulators for use in Operator Training”
certification of simulator fidelity (if used) is considered to be sufficient for the
initial stages of the beyond-design-basis external event scenario until the
current capability of the simulator model is exceeded. Full scope simulator
models will not be upgraded to accommodate FLEX training or drills.
5. Where appropriate, the integrated FLEX drills should be organized on a team
or crew basis and conducted periodically; with all time-sensitive actions to be
evaluated over a period of not more than eight years. It is not the intent to
connect to or operate permanently installed equipment during these drills and
demonstrations.
On page 20 of the Integrated Plan, the licensee stated that Dominion's Nuclear Training
Program will be revised to assure personnel proficiency in the mitigation of BDB events is
developed and maintained. These programs and controls will be developed and implemented in
accordance with the Systematic Approach to Training (SAT).
The licensee stated that initial and periodic training will be provided to site emergency response
leaders on BDB emergency response strategies and implementing guidelines. Personnel
2
The Systematic Approach to Training (SAT) is recommended.
Emergency response leaders are those utility emergency response personnel assigned leadership
roles, as defined by the Emergency Plan, for managing emergency response to design basis and beyonddesign-basis plant emergencies.
3
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assigned to direct the execution of mitigation strategies for BDB events will receive necessary
training to ensure familiarity with the associated tasks, considering available job aids,
instructions, and mitigation strategy time constraints.
The licensee stated that operator training for BDB event accident mitigation will not be given
undue weight in comparison with other training requirements. The testing/evaluation of
Operator knowledge and skills in this area will be similarly weighted. Operator training will
include use of equipment from the Regional Response Center.
The licensee stated that "ANSI/ANS 3.5, Nuclear Power Plant Simulators for use in Operator
Training" certification of simulator fidelity (if used) is considered to be sufficient for the initial
stages of the BDB external event scenario until the current capability of the simulator model is
exceeded. Full scope simulator models will not be upgraded to accommodate FLEX training or
drills.
The licensee stated that where appropriate, integrated FLEX drills will be organized on a team
or crew basis and conducted periodically; with all time-sensitive actions to be evaluated over a
period of not more than eight years. It is not required to connect/operate permanently installed
equipment during these drills.
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01 and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to training, if these
requirements are implemented as described.
3.4
OFFSITE RESOURCES
NEI 12-06, Section 12.2 lists the following minimum capabilities for offsite resources for which
each licensee should establish the availability of:
1) A capability to obtain equipment and commodities to sustain and backup the
site’s coping strategies.
2) Off-site equipment procurement, maintenance, testing, calibration, storage,
and control.
3) A provision to inspect and audit the contractual agreements to reasonably
assure the capabilities to deploy the FLEX strategies including unannounced
random inspections by the Nuclear Regulatory Commission.
4) Provisions to ensure that no single external event will preclude the capability
to supply the needed resources to the plant site.
5) Provisions to ensure that the off-site capability can be maintained for the life
of the plant.
6) Provisions to revise the required supplied equipment due to changes in the
FLEX strategies or plant equipment or equipment obsolescence.
7) The appropriate standard mechanical and electrical connections need to be
specified.
8) Provisions to ensure that the periodic maintenance, periodic maintenance
schedule, testing, and calibration of off-site equipment are
comparable/consistent with that of similar on-site FLEX equipment.
9) Provisions to ensure that equipment determined to be unavailable/nonoperational during maintenance or testing is either restored to operational
status or replaced with appropriate alternative equipment within 90 days.
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10) Provision to ensure that reasonable supplies of spare parts for the off-site
equipment are readily available if needed. The intent of this provision is to
reduce the likelihood of extended equipment maintenance (requiring in
excess of 90 days for returning the equipment to operational status).
On page 21 of the Integrated Plan, the licensee stated that the industry will establish two RRCs
to support utilities during BDB events. Dominion has established contracts with the PEICo to
participate in the process for support of the RRCs as required. Each RRC will hold five sets of
equipment, four of which will be able to be fully deployed when requested, the fifth set will have
equipment in a maintenance cycle. In addition, on-site BDB equipment hose and cable end
fittings are standardized with the equipment supplied from the RRC. Equipment will be moved
from an RRC to a local Assembly Area, established by the SAFER team and the utility.
Communications will be established between the affected nuclear site and the SAFER team and
required equipment moved to the site as needed. First arriving equipment, as established during
development of the nuclear site's playbook, will be delivered to the site within 24 hours from the
initial request.
The implementation of Guidelines 2 through 10 above is identified as Confirmatory Item 3.4.A,
in Section 4.2
The licensee’s approach described above, as currently understood, is consistent with the
guidance found in NEI 12-06, as endorsed by JLD-ISG-2012-01 and provides reasonable
assurance that the requirements of Order EA-12-049 will be met with respect to off site
resources, if these requirements are implemented as described.
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4.0
OPEN AND CONFIRMATORY ITEMS
4.1
OPEN ITEMS
Item Number
Description
3.2.1.2.B
Demonstration of the acceptability of the use the Flowserve
N-9000 seals with the Abeyance feature and validation of an
acceptable leakage rate for these seals.
The PWROG submitted to NRC a position paper, dated
August 15, 2013, which provides test data regarding boric
acid mixing under single-phase natural circulation conditions
and outlined applicability conditions intended to ensure that
boric acid addition and mixing would occur under conditions
similar to those for which boric acid mixing data is available.
During the audit process, the licensee informed the NRC staff
that its boric acid mixing model is based on the PWROG
method. Since the audit discussions, the NRC endorsed the
PWROG guidance with several clarifications in the letter
dated January 8, 2014. The licensee should address the
clarifications alignment with the NRC endorsement letter for
the development of an adequate model for determining the
mixing of boric acid in the reactor coolant system during
natural circulation with the potential for two-phase flow
conditions.
3.2.1.8.A
4.2
Notes
CONFIRMATORY ITEMS
Item Number
Description
3.1.1.1.A
Storage & Protection of FLEX equipment – Confirm final
design of FLEX storage structure conforms to NEI 12-06,
Sections 5.3.1, 6.2.3.1, 7.3.1, and 8.3.1 for storage
considerations for the hazards applicable to North Anna.
Procedural Interface Considerations (Seismic) – Confirm
FLEX support guideline to provide operators with direction on
how to establish alternate monitoring and control capabilities.
Off-Site Resources – Confirm RRC local staging area,
evaluation of access routes, and method of transportation to
the site.
Clarify whether the site intends to use 107 degrees F or the
values recommended in NEI 12-06 Section 9.2 as the basis
for protection and deployment strategies of FLEX equipment.
In the Integrated Plan, the licensee did not address
considerations for any manual actions required by plant
personnel is high temperature conditions as recommended in
NEI 12-06, Section 9.3.2. Discuss effects of high
temperatures on any manual action performed by plant
3.1.1.3.A
3.1.1.4.A
3.1.5
3.1.5.2.A
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Notes
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3.2.1.1.A
3.2.1.1.B
3.2.1.1.C
3.2.1.2.C
3.2.1.6.A
3.2.1.8.B
personnel and any applicable contingencies and any related
procedural changes or enhancements.
Reliance on the NOTRUMP code for the ELAP analysis of
Westinghouse plants is limited to the flow conditions before
reflux condensation initiates. Specify an acceptable definition
for reflux condensation cooling.
Confirmation that the generic analysis in Section 5.2.1 of
WCAP-17601-P is applicable or bounding with respect to
North Anna for an appropriate figure of merit for defining entry
into the reflux condensation cooling mode.
Confirm the consistency of the margin imposed to prevent
accumulator nitrogen injection with the cooldown terminus
assumed in WCAP-17601-P
(1)
Confirm that stresses resulting from a cooldown of the
RCS will not result in the failure of seal materials.
(2)
As applicable, confirm that reestablishing cooling to
the seals will not result in increased leakage due to thermal
shock.
Sequence of Events – Confirm that the final timeline has
been time validated after detailed designs are completed and
procedures are developed. The results will be provided in a
future 6-month update.
Completion of calculations demonstrating adequate shutdown
margin for North Anna in ELAP scenarios with and without
seal leakage.
3.2.1.8.C
Confirm that shutdown margin calculations will be verified to
remain bounding for future operating cycles and clarify the
method that will be used to make this determination.
3.2.1.9.A
North Anna will purchase and store two BDB RCS Injection
Pumps for use in the Phase 2 RCS Inventory strategy.
However, the licensee did not clarify how the two BDB RCS
injection pumps conform to NEI 12-06, paragraph following
Section 3.2.2, Guideline 15 which states in part: “In order to
ensure reliability and availability of the FLEX equipment
required to meet these capabilities, the site should have
sufficient equipment to address all functions at all units onsite, plus one additional spare, i.e., N+1 capability, where N is
the number of units on-site.”
3.2.1.9.B
Confirm completion of calculations documenting the AFW
supply, SFP makeup, and RCS inventory hydraulic analysis.
SFP venting – Provide a technical justification that confirms
opening of the roll-up doors would provide an adequate
ventilation path for the SFP area.
Containment – Confirm containment analysis to determine
any containment temperature and pressure actions beyond 7
days.
Ventilation – Equipment Cooling – Confirm development of
the ventilation strategy.
3.2.2.A
3.2.3.A
3.2.4.2.A
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3.2.4.2.B
3.2.4.4.A
3.2.4.4.B
3.2.4.8.A
3.2.4.9.A
3.4.A
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Battery rooms are not modeled in the loss of ventilation
transient analysis model. Therefore, it appears that there is
no analysis or calculation to demonstrate the adequacy of the
battery room ventilation.
Verify the lighting study validates the adequacy of
supplemental lighting and the adequacy and practicality of
using portable lighting to perform FLEX strategy actions. The
lighting study is being tracked by licensee Open Item 17
Communications - Review the licensee’s proposed
enhancements and interim measures to the site’s
communications systems and that they have been completed.
Electrical Power Sources – Confirm load calculations for the
phase 2 and 3 FLEX generators will support supplied loads.
Fuel Supplies – Confirm the adequacy of the fuel
consumption evaluation. Confirm that the procedural
guidance governing re-fueling strategies addresses: (a) how
the quality of the fuel oil and gasoline supplies will be
controlled in order to ensure proper diesel or gasolinepowered FLEX equipment operation, (b) available sources of
gasoline and how those sources will be protected to ensure
availability following a BDB event, and (c) if the onsite fuel
capacity provides an indefinite supply of fuel or if the RRC is
capable of providing an indefinite, ongoing supply of fuel
(both diesel and gasoline).
NEI 12-06, Section 12.2 lists minimum capabilities for offsite
resources for which each licensee should establish the
availability. The licensee did not discuss implementation of
consideration 2 through 10 in NEI 12-06, Section 12.2.
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